TB-500: The Definitive Guide

What is TB-500?

TB-500 is a lab-made peptide, a chain of seven amino acids, that people inject hoping to recover faster from tendon, ligament and muscle injuries. It copies a short stretch of thymosin beta-4, a protein made by most of the body's cells, but it has never been studied in people.

Amino acids are the building blocks of proteins, and a peptide is a short chain of them. Chemically, TB-500 is the amino acids at positions 17 to 23 of thymosin beta-4 (leucine, lysine, lysine, threonine, glutamic acid, threonine and glutamine, written Ac-LKKTETQ), with an extra chemical cap called an acetyl group on the first one. Thymosin beta-4 itself is 43 amino acids long. [1], [2], [3]

The name is a trade name, not a scientific one. TB-500 first appeared around 2011 as a veterinary product marketed to racehorse and greyhound trainers, and anti-doping laboratories identified what was in it a year later. [1], [3], [2]

Thymosin beta-4 is a chain of 43 amino acids made by the body. Positions 1 to 4, called Ac-SDKP, are a separately studied anti-inflammatory region and are not part of TB-500. Positions 17 to 23 are the stretch copied as TB-500. TB-500 is a lab-made copy of those seven amino acids, leucine, lysine, lysine, threonine, glutamic acid, threonine and glutamine (L-K-K-T-E-T-Q), with an acetyl cap on the first and a free acid at the end. Its first six, LKKTET, match thymosin beta-4’s actin-binding stretch. Identity: 7 amino acids, C38H68N10O14, 889.01 g/mol, lab-made. A vial labelled TB-500 may contain either the 7-amino-acid fragment, which is TB-500 as defined by the FDA and anti-doping laboratories, or full-length thymosin beta-4, which is often sold under the same name. No public study measures how often each is sold. Bead positions show order, not 3D structure; only TB-500’s letters are shown.

Doserly

TB-500 is 7 of thymosin beta-4’s 43 amino acids

Chemistry and regulator identity data

Thymosin beta-4made by the body · 43 amino acids1–4: Ac-SDKP, a separately studied anti-inflammatory region, not in TB-50017–23: the stretch copied as TB-500

TB-500lab-made copy of positions 17–23 with an acetyl capAcL (Leu)K (Lys)K (Lys)T (Thr)E (Glu)T (Thr)Q (Gln)–OHLeu-Lys-Lys-Thr-Glu-Thr-GlnLKKTET (1–6) matches thymosin beta-4’s actin-binding stretch.7 amino acids · C₃₈H₆₈N₁₀O₁₄ · 889.01 g/mol · lab-made

What a vial labelled “TB-500” may containThe 7-amino-acid fragmentTB-500 as defined by the FDA and anti-doping laboratoriesorFull-length thymosin beta-443 amino acids; often sold under the same nameNo public study measures how often each is sold.

Bead positions show order, not 3D structure; only TB-500’s seven amino acids are lettered. Sources: FDA TB-500 evaluation (2026); anti-doping analysis (2012).

TB-500 and thymosin beta-4 are different molecules: research on one does not automatically apply to the other.

The key word is investigational. TB-500 is not part of any approved medicine in the United States, Canada, Australia, the United Kingdom or the European Union. When the FDA reviewed it in 2026, it found no published report of anyone ever being given TB-500 in a study, and no standard safety tests in animals. [1]

Is TB-500 the same as thymosin beta-4?

No, although they are often sold as if they were. Thymosin beta-4 (often shortened to TB4) is the whole 43-amino-acid protein; TB-500 is a capped 7-amino-acid piece of it. Many product listings are titled "TB-500 (Thymosin Beta-4)", and some print the chemical registry number of the full protein on a TB-500 label. [1], [4], [5]

This matters in three ways. First, almost all the research people quote for TB-500, including every human trial, used full-length thymosin beta-4. Second, the FDA warns that results for an uncapped fragment cannot simply be carried over to the capped one, because the acetyl cap changes how a peptide behaves. Third, a buyer usually cannot tell which molecule is in a vial, and even sellers and calculators mix them up: one popular dosing calculator describes TB-500 as a 43-amino-acid peptide. No public study measures how often products sold as TB-500 contain the fragment rather than the full protein. [1], [6], [7]

In this guide, TB-500 means the 7-amino-acid fragment, and thymosin beta-4 means the full protein. Where a study or report used thymosin beta-4, we say so. For a side-by-side comparison, including which molecule has been tested for which use, see how TB-500 differs from thymosin beta-4.

Typical TB-500 Protocols

Read these cautions before the numbers. No amount of TB-500 has ever been tested in a person. These schedules describe what protocol websites publish, and their two-phase pattern traces back to veterinary and forum practice, not to a study. [9], [8], [1]

• The vial may not contain what the label says. Some products sold as TB-500 contain full-length thymosin beta-4, a different molecule, and how often this happens is unknown. In a 2026 analysis of consumer-submitted test results (a preprint, not yet peer reviewed), TB-500 had the highest rate of samples that did not contain the stated peptide (1 in 10) and the lowest purity of 14 peptides. [10], [4]
• Not studied in pregnancy, while breastfeeding or trying to conceive, in under-18s, or in people with a cancer history. No reproductive, cancer or standard toxicity studies exist, and thymosin beta-4 helps drive tumour spread in some animal models. [1], [11]
• Tell your surgeon, and ask before combining it with blood thinners. Nothing is known about bleeding or clotting in people; one pig study found that high doses of thymosin beta-4 changed blood-vessel tone and weakened clots when combined with an antiplatelet drug in the lab. [12]
• Milligrams, micrograms and syringe units are easy to confuse. 1 mg is 1,000 mcg, and a "unit" on an insulin syringe measures liquid, not TB-500. Check any amount with the reconstitution calculator (worked example below).
• It is banned in sport at all times. [13]

The most common protocol in the reviewed sources is 2–2.5 mg by subcutaneous injection twice a week for 4–6 weeks (a weekly total of 4–5 mg), then about 2 mg once a week or every two weeks. [8], [9], [14], [15], [16], [17], [18]

Loading and maintenance The two phases

Almost every source uses a loading phase of more frequent injections for 4–6 weeks, then a maintenance phase once a week or every two weeks for another 4–8 weeks. Loading injections are usually spaced 3–4 days apart, for example Monday and Thursday. [8], [15], [17], [14]

Titration Changing the amount in steps

Most sources start at the full loading amount. A gentler start also appears: 1 mg twice a week for two weeks, then 2 mg twice a week, described as a clinician's judgement call rather than something tested. Another source simply advises the lowest tier for a first course. [16], [8]

Breaks and cycles

The same source that supplies the table describes whole cycles of 8–14 weeks (loading plus maintenance), then 4–8 weeks off before reassessing, and advises against running it for more than 14–16 weeks without a break. It calls the break a precaution rather than something based on reported side effects. [8]

Read the units: these amounts are in milligrams (mg); 1 mg equals 1,000 micrograms (mcg). The weekly total adds up every injection in a week, which is the fairest way to compare a twice-weekly schedule with a daily one. The amounts refer to TB-500 alone, not to the total weight of a blend such as the Wolverine stack (see blends).

Each row is a complete schedule from one published source, so its amount and duration belong together: the high example is a shorter course, not a longer one at a higher amount. Low, mid and high are alternatives, not steps to move through. These schedules come from protocol websites rather than any study in people; the cited references give the full details.

Where protocols differ: daily schedules, loading, breaks and blends ↓

What about daily schedules?

A second group of sources gives TB-500 every day in smaller amounts, the way BPC-157 is usually given. These are complete schedules from three different pages.

Daily and twice-weekly schedules can reach similar weekly totals by very different routes: 500 mcg every day is 3.5 mg a week, close to the 4–5 mg of twice-weekly loading. Nobody has compared the two in people or animals. The disagreement section explains where the split comes from.

What about blends like the Wolverine stack?

TB-500 is most often used alongside BPC-157, either from a pre-mixed vial (commonly sold as the "Wolverine" stack or blend) or from two separate vials. In a blend, the number on the label is the total of both peptides, so the TB-500 part of each dose is only a fraction of what is drawn up. The rows below come from one protocol page that describes both formats. [28]

One clinic that dispenses the pre-mixed vial describes a similar rhythm: once a day for five days, then two days off, in one-month cycles of 20 injections, up to three cycles in a row before a two-month break, with the amount set by the prescriber. Four-peptide blends such as KLOW add GHK-Cu and KPV; in one common KLOW vial label (50 mg GHK-Cu with 10 mg each of BPC-157, TB-500 and KPV), TB-500 is only one eighth of every dose. [29], [30], [31] See the Doserly guides to the Wolverine blend, KLOW and GLOW.

What is TB-500 commonly used for?

People usually look into TB-500 when an injury is slow to settle: a tendon that flares every time they train, a partly torn shoulder muscle, a sprained ankle that still hurts months later, or a sore knee that limits everyday life. Most use it together with BPC-157, and often alongside physiotherapy, rest or other medicines. [32], [33], [34]

Websites also sell it for wound healing, hair growth, heart and brain health, endurance, muscle growth and inflammation. The FDA lists all of these as uses TB-500 is marketed for, while finding no study in which it was given to people for any of them. The sections below describe what people hope for and report; they do not establish that TB-500 treats any condition. [1]

Tendon, ligament and muscle injuries

This is the main reason people use TB-500. The hoped-for result is practical: less pain when lifting, running or reaching, and a return to training without the injury flaring. Common targets in public forums are elbow tendinitis (tennis and golfer's elbow), shoulder and rotator cuff problems, Achilles and hamstring trouble, plantar fasciitis (heel pain from the tissue under the foot) and muscle tears. [32], [35], [36], [37]

The research behind this hope is thin. There is one animal study of this kind, and it used a commercial product sold as TB-500 without testing which molecule it contained. In rats with surgically repaired Achilles tendons, daily injections into the abdominal cavity for four weeks gave stronger tendons and better tissue scores than no treatment, while BPC-157 alone did not reach significance on the main scores. Each group had eight rats, but only four tendons per group were tested for strength and four for tissue changes. [38]

For full-length thymosin beta-4, a rat knee-ligament study and a mouse fracture study reported stronger, better-organised repairs, but in mice with a muscle-wasting disease, six months of thymosin beta-4 increased regenerating muscle fibres without improving strength. No study in people has tested either molecule for a tendon, ligament or muscle injury. [39], [40], [41]

Joint pain and arthritis

People also use it for knee and shoulder arthritis, "creaky" joints and long-standing hip pain. Public reports here are mixed: some describe easier movement within weeks, while several people with labral tears, joint arthritis or cartilage damage report no change. [42], [43], [44], [32], [45]

There is an odd twist in the research. People with knee osteoarthritis have higher thymosin beta-4 levels in their blood and joint fluid than people without it, and the levels rise with severity; joint fluid in rheumatoid arthritis contains even more. That is an association, not a cause or a treatment effect, but it means "topping up" thymosin beta-4 in a sore joint is not a simple idea. [46], [47]

Recovery after surgery

Some people use TB-500, usually with BPC-157, after operations such as hernia repair, ligament or tendon repair, or fracture fixation. The accounts often describe surgeons surprised by fast healing, but the same people also had the surgery itself, rehabilitation and sometimes growth hormone, testosterone or other drugs, so the peptide's share cannot be separated. [33], [48]

Protocol sources disagree about timing: one suggests starting 2–4 weeks after surgery and discussing it with the surgeon. In community education groups, some members say their surgeons asked them to stop all peptides one to two weeks before an operation. [8]

Skin wounds, eyes and hair

Most of the human research sits here, but it used thymosin beta-4 gels and eye drops, not TB-500: gels on leg ulcers, pressure sores and the fragile skin of epidermolysis bullosa (a genetic blistering disease), and drops on dry eye and a hard-to-heal corneal condition. Results were mostly modest or missed their main goal; see the details. [49], [50], [51], [52], [53]

Hair growth is a smaller interest. In mice, thymosin beta-4 made hair grow faster, and mice bred to overproduce it regrew hair faster than normal mice. There is no human hair study. A few forum users describe new body hair on TB-500, including one who self-reported fine, pale hair growth on two different products. [54], [55], [56]

Heart, brain and other claims

Claims about heart repair, stroke recovery, nerve regeneration and "anti-aging" come from animal work with full-length thymosin beta-4. In people, an intravenous (IV) form of the protein given after a heart attack did not reduce overall heart-muscle damage; only a subgroup treated within eight hours did better, a finding that needs confirming. No human study has tested TB-500 for any of these uses. [57], [58], [1]

See the human study results or explore the supporting animal research.

How is TB-500 different from thymosin beta-4?

Thymosin beta-4 is the whole protein the body makes; TB-500 is a small lab-made copy of one stretch of it. They are different molecules with different evidence behind them. No study has compared TB-500 as sold (capped and injected) with thymosin beta-4 in people; the only side-by-side animal work used the uncapped sequence on skin wounds in mice, where it did about as well as the full protein. [1], [105]

Weights from the FDA's TB-500 review and PubChem. WADA's Prohibited List names "Thymosin-β4 and its derivatives e.g. TB-500". [1], [175], [13]

Why are they sold as if they were the same?

• Labels and listings. Many products are titled "TB-500 (Thymosin Beta-4)", some TB-500 labels carry the full protein's registry number, and one popular dosing calculator describes TB-500 as a 43-amino-acid peptide. [4], [5], [7]
• Official descriptions. New Zealand's medicines regulator calls TB-500 the "synthetic form" of thymosin beta-4. [131] The group that nominated TB-500 for FDA review supported it with three lab and animal papers from thymosin beta-4 research, two of which tested the uncapped sequence rather than TB-500 itself; the FDA noted that none involved a compounded TB-500 product. [1]
• Price. One comparison site describes the full protein as "significantly more expensive per mg", and forum users put it at roughly two to four times the price of the fragment. [176], [177], [178]

A label cannot tell you which molecule is in a vial. A certificate of analysis that names the sequence or the measured mass can: about 889 g/mol for TB-500 (about 949 for its acetate salt form) and about 4,963 g/mol for the full protein, though it describes only the batch tested. [1], [175]

The same number of milligrams is not the same amount of molecule either. Thymosin beta-4 is about 5.6 times heavier, so 2 mg of it holds about 0.40 micromoles against about 2.25 micromoles in 2 mg of TB-500. That does not make either one "stronger", because the two have not been shown to act alike, but it does mean a schedule written for one cannot simply be reused for the other. [1], [175]

Which molecule has been tested for which use?

This compares where each molecule has actually been tested. It is not a recommendation to use either one.

In short, the human research belongs to thymosin beta-4 used on the eye or skin or given by IV; none of it tested either molecule as a subcutaneous injection for an injury. Anyone weighing either product for an injury is relying on animal studies and personal accounts, whichever name is on the vial. For the full protein's protocols, trials and risks, read Doserly's thymosin beta-4 guide and its side-by-side comparison.

Where do TB-500 protocols differ?

The headline pattern is easy to summarise; the details are not. Sources disagree about whether TB-500 should be given twice a week or every day, whether to start with a loading phase, how long to keep going, and even which molecule is in the vial. Here is what those differences mean when reading a protocol.

Is the number for one injection, one day or one week?

A dose is the amount given each time; a daily total or weekly total adds them up. 2.5 mg twice a week means 5 mg a week. By contrast, 500 mcg every day means 3.5 mg a week, and 5 mg twice a week means 10 mg. Two descriptions that look similar can differ several-fold once you add them up. [8], [26], [14]

Some pages give only a weekly figure, such as "5–10 mg a week split into two injections" or "4–6 mg per week split twice weekly", and some maintenance figures such as "2–2.5 mg per week" could be one injection or several. Check whether each number is per injection, per day or per week before comparing it with anything else. [59], [60], [61]

Blends add a further step: the amount drawn from a pre-mixed vial is the total of every peptide in it. See the blend table.

Twice a week or every day?

Both are common, and the split follows the confusion over what TB-500 is. The twice-weekly "loading then maintenance" style dominates dosing websites. The daily style of 250–1,000 mcg a day dominates blends and prescriptions from clinics, and some public accounts describe doctors prescribing compounded "thymosin beta-4", for example about 500 mcg a day, or 600 mcg every third day. [8], [28], [27], [62], [63]

Weekly amounts of TB-500 in published schedules, worked out from each page’s stated amount and frequency. One source’s tiers (PeptideWiki): twice a week, low loading, 2 mg twice for 4 to 6 weeks, 4 mg a week; twice a week, mid loading, 2.5 mg twice for 4 to 6 weeks, 5 mg a week; three times a week, high loading, 2.5 mg three times for 4 weeks, 7.5 mg a week; maintenance after loading, 2 mg once a week or every 2 weeks, 1 to 2 mg a week. Other published schedules: daily TB-500 alone, 250 to 1,000 mcg a day, 1.75 to 7 mg a week; pre-mixed 1:1 Wolverine blend, 0.5 to 2 mg of blend a day on 5 to 7 days a week, half of it TB-500, 1.25 to 7 mg a week; a severe-injury option on some pages, 5 mg twice a week, 10 mg a week. The schedules differ about tenfold. None of these amounts has been tested in people.

Doserly

Same name, very different weekly amounts

Protocol sources (websites) · never tested in people

One source’s tiers (PeptideWiki)

Twice a week, low loading

2 mg × 2 · for 4–6 weeks4 mg a week

Twice a week, mid loading

2.5 mg × 2 · for 4–6 weeks5 mg a week

Three times a week, high loading

2.5 mg × 3 · for 4 weeks7.5 mg a week

Maintenance after loading

2 mg once a week or every 2 weeks1–2 mg a week

Other published schedules

Daily TB-500 alone

250–1,000 mcg a day1.75–7 mg a week

Pre-mixed 1:1 blend (Wolverine)

0.5–2 mg of blend a day, 5–7 days a week; half is TB-5001.25–7 mg a week

“Severe injury” option on some pages

5 mg × 210 mg a week

05 mg10 mg a weekWeekly totals are arithmetic from each page’s stated amount and frequency (PeptideWiki; three daily charts; one blend chart; two 5 mg pages).

Schedules sold under the same name differ about tenfold, from 1 mg to 10 mg of TB-500 a week. None has been tested in people.

The reasons given for each style contradict one another, and none rests on a measurement. Some sources say TB-500 lasts for days, so twice a week is enough. One page says the fragment is shorter-acting than the full protein, so it should be given daily. Another argues the familiar 2–4 mg figure is really a thymosin beta-4 number and derives 1–2.5 mg two or three times a week, with no loading phase, for the fragment; a second page reaches 1–1.5 mg two or three times a week. In community education groups, one educator tells members that most vials are really thymosin beta-4 and should be dosed at 0.5–1 mg a day, while other groups teach the twice-weekly schedule. [64], [25], [65], [66]

The only measured figures cut against the "lasts for days" claim; see how long TB-500 lasts in the body.

Do sources start low, or load first?

Most sources do the opposite of starting low: they begin with the most frequent injections (the loading phase) and then cut back. The usual explanation is that loading "saturates" tissue, but no published study has shown TB-500 building up in tissue, in people or animals. [8], [15], [1]

A few sources describe a gentler start. One telehealth page describes some clinicians starting at 1 mg twice a week for two weeks before moving to 2 mg twice a week. A daily chart climbs from 500 mcg to 1,000 mcg over 12 weeks, while another daily page does the reverse, starting at 500 mcg and dropping to 250 mcg. [16], [27], [25]

These are different examples, not pieces of one protocol. There is no established rule that no improvement at a lower amount means a higher amount will work, although in public forums and community education groups people often raise the amount after a few weeks without change. [67], [32]

How many weeks, and what happens between cycles?

A course is the period of repeated use; a cycle is that course plus a planned break. Published patterns include:

• Loading plus maintenance: 4–6 weeks of loading, then 4–8 weeks of maintenance, for a whole cycle of 8–14 weeks, followed by 4–8 weeks off. [8]
• Daily courses: 6 weeks; 8 weeks on and 8 weeks off; or 12 weeks with rising amounts. [25], [26], [27]
• Clinic blend cycles: one-month cycles of five days on and two off, up to three in a row, then a two-month break. [29]
• Until healed: one page gives 2.5 mg twice a week "until healed", with no end point. [17]
• The original veterinary product: one vial weekly for six weeks, then monthly with no end date. [19]

In community education groups, the advice runs from a four-week maximum with long breaks to daily use for most of a year, and some people describe using it continuously for months or years. The reasons given for breaks, such as "resetting receptors", have not been tested for TB-500; one protocol source calls its break a precaution, not a response to known side effects. [8], [68]

Why do some pages scale the dose by body weight?

A few pages start from an animal product and scale it to a person. One widely shared article turns a 5 mg greyhound dose from a veterinary maker into "about 7.66 mg per week for six weeks" for a 200-pound person, and a clinic blog repeats 4–7.66 mg a week. Others suggest 0.03–0.05 mg per kg twice a week, or 30–60 mcg per kg per injection. [69], [70], [16], [71]

That arithmetic produces a number; it is not a dose tested in people. Scaling a dog or horse product label to a human by weight assumes the peptide behaves the same way in both species, which no study has checked.

How do milligrams convert to syringe units?

Many people meet "units" on an insulin syringe. A U-100 syringe holds 100 units per millilitre, so units measure volume, not an amount of TB-500. How much TB-500 each unit holds depends on how much liquid was added when the powder was mixed (reconstituted).

For example, a 5 mg vial mixed with 2 mL gives 2.5 mg per mL, or 25 mcg per unit, so a 2 mg injection is 80 units (0.8 mL) and a 2.5 mg injection is a full 100-unit syringe. The same 2.5 mg from a 10 mg vial mixed with 2 mL is only 50 units. [8], [18]

Mistakes happen at every step. In one public thread, a person first described their prescribed dose as "2 ml" of a 3 mg per mL product, which would be 6 mg, before the thread worked out that the intended amount was about 500 mcg. Blends make it harder still, because the concentration on the label is the total of all the peptides. Doserly's reconstitution calculator works this out for any vial and shows each step. [62]

What happens when you stop TB-500?

This has not been studied. No study has looked for withdrawal effects or a rebound after stopping TB-500, and the FDA found no human data of any kind. That is an absence of data, not proof that none exist. [1]

• In a thymosin beta-4 eye-drop trial, none of the corneal wounds that healed on treatment had reopened two weeks after the drops stopped. That tells us about eye drops of the full protein, not about injected TB-500. [53]
• Public accounts point both ways. One person's ankle pain after sport disappeared within a week of starting, then returned during a two-month break; another felt about half the old soreness come back after stopping a six-week course after hip-tendon surgery; a shoulder improved in two weeks and relapsed after stopping at four. Others say knee or hip pain stayed away for months or even two years. [68], [37], [79], [80], [81]
• In community education groups, several members describe pain returning within one or two weeks of stopping, and nobody described withdrawal symptoms.

As one forum commenter pointed out, pain that comes back soon after stopping fits short-term symptom relief better than repair. A single account cannot settle which is happening. The breaks that protocols describe are a convention, not a response to known withdrawal effects. [68], [8]

Do injected, oral and nasal TB-500 behave the same way?

Nobody knows, because TB-500 has never been measured in people by any route: there are no human pharmacokinetic studies of how the body absorbs, moves and removes it. Almost every protocol uses subcutaneous injection (into the fatty layer under the skin); some pages and clinics also describe intramuscular injection (into a muscle), which is how the pharmacy that nominated it to the FDA proposed to supply it, at 3 mg per mL. [8], [17], [22], [1]

What is known comes from animals and laboratory tests. In horses given a subcutaneous injection and in rats given an injection into the abdominal cavity, TB-500 reached the bloodstream and was quickly cut into smaller pieces. Because no study gave it straight into a vein for comparison, even the animal bioavailability (how much reaches the blood) is unknown. In the lab, human liver, kidney and blood-serum preparations also broke TB-500 into several smaller pieces. [1], [3], [82], [83], [84]

• Subcutaneous or intramuscular injection: the only routes with any animal data. No study has compared the two.
• Swallowed (oral capsules): no data in any species. Short peptides are broken down by digestive enzymes, and the lab findings above suggest TB-500 would be no exception. In community education groups, members generally treat oral "Wolverine" capsules as unlikely to work outside the gut, although one teaching card lists the same amount by mouth as by injection. [84]
• Nasal sprays: no data in any species.
• Eye drops and skin gels: tested in people only for full-length thymosin beta-4. In an animal model of burned corneas, a gel built from a chemically modified peptide containing the TB-500 sequence was tested, not TB-500 itself. [52], [49], [85]

How long does TB-500 last in the body?

Half-life is the time it takes for the level in the blood to fall by half. It has never been measured for TB-500 in people. [1]

The closest data are from animals. After a single 10 mg subcutaneous injection in horses, TB-500 peaked in the blood at 1–2 hours at very low levels (0.05–0.08 ng per mL) and could no longer be measured 6–10 hours later. Its breakdown products (metabolites) last longer: in rats, one of them was still detectable in urine 72 hours after a dose, and anti-doping laboratories use such fragments to catch its use in horses. [1], [3], [82], [19]

For the full protein in people, IV thymosin beta-4 fell by half in 0.5–2 hours and did not build up over 10 days of daily infusions. That is a different molecule and route, but it is the only human measurement. [86]

Websites quote half-lives from "about 2 hours" to "two to four days" to justify their schedules, and figures up to a week circulate in community education groups. None comes from a published measurement of TB-500, and a half-life says nothing, by itself, about how long an effect lasts. [7], [59], [64]

Should TB-500 be injected near the injury?

Sources split. Many say TB-500 acts throughout the body, so an injection in the abdomen reaches a shoulder or knee just as well; some people in public forums instead switch to injecting near the sore area and describe it working better. No study, in people or animals, has compared the two. In the rat tendon study, the product was injected into the abdominal cavity, far from the tendon. [8], [26], [17], [43], [42], [87], [38]

In community education groups, educators warn against injecting into a joint, and point out that injecting near an injury adds risks of hitting a blood vessel or nerve without any shown benefit.

Which form of TB-500 is in the vial?

TB-500 is sold under one name in several forms, and the FDA judged neither of the two it reviewed to be well characterised. [1]

Weights and registry details from the FDA review. [1], [4]

The example certificate of analysis the FDA examined for the free base tested appearance, identity and purity, but not the actual amount of peptide, impurities, bacterial toxins (endotoxins) or clumping (aggregation); for the acetate, the nature of impurities present at up to 1% was unknown. One public-forum user found the registry number of the full protein printed on a vial sold as TB-500. [1], [5]

How should TB-500 be stored, and how long does it last?

No one has published a stability study of a TB-500 product, so there is no tested use-by date for a mixed vial. Storage advice comes from suppliers and protocol pages, not from a medicine label. [1]

• Powder, before mixing. TB-500 is sold as a freeze-dried powder. Supplier data quoted by the FDA say to keep the free base sealed, dry, dark and under nitrogen gas, at −80 °C for up to 2 years or −20 °C for up to 1 year. For the acetate, one certificate says 2–8 °C, while other public information says below −15 °C, away from light. [1]
• After mixing. The same supplier data give 6 months at −80 °C or 1 month at −20 °C for TB-500 in solution. Protocol pages instead say to keep a vial mixed with bacteriostatic water in the fridge (2–8 °C) and use it within 3–4 weeks, and some add never to freeze it. [1], [8], [27]
• Room temperature. One clinic page claims about ten weeks at room temperature, with no data behind it. Company-run tests relayed in community education groups, on material identified as full-length thymosin beta-4, suggested much faster loss of strength at room temperature than in a fridge; those are single-batch vendor tests, not published studies. For comparison, a recombinant thymosin beta-4 being developed as a medicine is stored in a fridge (2–8 °C). [23], [75]

Storage is not only about strength. The FDA notes that peptides like TB-500 are very sensitive to heat, acidity and handling, which can make them break down or clump, and that clumps and impurities in an injected peptide can trigger an immune reaction. This guide does not cover mixing or injection technique; the Academy note below covers practical handling. [1]

What do we actually know about TB-500 in people?

Nothing directly. The FDA searched the medical literature, trial registries and its own adverse-event databases and found no study, case report or other record of TB-500 being given to people. A 2026 scoping review (a broad map of the research, not yet peer reviewed) screened 1,772 records on thymosin beta-4 and TB-500 in tissue healing, included 80 studies, and found direct TB-500 evidence in only one of them. [1], [6]

Three 2026 sports-medicine reviews reach the same conclusion: promising animal work, very little human data, and real uncertainty about safety. What does exist is a set of human trials, several of them controlled, of full-length thymosin beta-4, mostly as eye drops, skin gels and IV infusions. [88], [89], [90]

Where TB-500 and full-length thymosin beta-4 have been tested, by topic. Skin wounds: in a scratch test on skin cells, TB-500 had no effect while a breakdown product helped; in aged mice, the uncapped fragment, which is not TB-500 itself, helped wounds close; full-length thymosin beta-4 sped healing of rat and mouse wounds and burns, and gels for leg ulcers, pressure sores and a blistering skin disease were tested in small human trials with inconclusive results. Eye surface: no TB-500 cell studies; in animals, a gel made from a modified peptide containing the TB-500 sequence, not TB-500 itself, helped burned corneas; thymosin beta-4 sped healing of mouse corneal chemical burns, and in people its eye drops mostly missed their main goals in dry-eye trials, and a corneal-wound trial was not significant at 4 weeks. Tendon, ligament, bone and muscle: no TB-500 cell studies; in one rat study of a product sold as TB-500, whose identity was not tested, repaired Achilles tendons were stronger at 4 weeks; thymosin beta-4 gave stronger repair in rat ligament and mouse fracture studies but no strength gain in mice with a muscle disease; no human studies. Heart: no TB-500 studies; thymosin beta-4 improved heart function in mice but gave no protection in pigs, and IV infusions after a heart attack in 96 people did not reduce overall damage. Brain and nerves: TB-500 reduced damage and inflammation in nerve and immune cells, and improved memory tests in Alzheimer’s-model mice without changing plaque; thymosin beta-4 improved function after stroke in rats, but not in aged rats; no human studies. Safety: TB-500 caused no damage to skin cells in a dish, and the FDA found no standard safety or cancer studies; for thymosin beta-4, cancer-model results are mixed and high doses weakened clots in pigs when combined with an antiplatelet drug; in people, IV thymosin beta-4 in 124 healthy volunteers across two studies caused no serious adverse events. TB-500 in people: 0 studies; the one registry record that names TB-500 describes itself as fictional.

Doserly

What has been tested, and on which molecule?

Cell, animal and human research, by molecule

Skin wounds

TB-500CellsScratch test: TB-500 no effect; a breakdown product helpedAnimalsAged mice: uncapped fragment helped wounds closeUncapped, so not TB-500 itselfPeople0 studiesFull-length thymosin beta-4Cells and animalsRat and mouse wounds and burns: faster healingPeopleGels for leg ulcers, pressure sores, blistering skin: small trials, inconclusive

Eye surface

TB-500CellsNone foundAnimalsBurned corneas: a TB-500-sequence gel helpedModified peptide, not TB-500People0 studiesFull-length thymosin beta-4Cells and animalsMouse chemical burn of the cornea: faster healingPeopleEye drops: dry-eye trials mostly missed main goals; corneal-wound trial not significant at 4 weeks

Tendon, ligament, bone, muscle

TB-500CellsNone foundAnimalsRat Achilles repair stronger at 4 weeksProduct identity not testedPeople0 studiesFull-length thymosin beta-4Cells and animalsRat ligament, mouse fracture: stronger repair; muscle-disease mice: no strength gainPeopleNone found

Heart

TB-500CellsNone foundAnimalsNone foundPeople0 studiesFull-length thymosin beta-4Cells and animalsMice: better heart function; pigs: no protectionPeopleIV after heart attack (96 people): overall damage not reduced

Brain and nerves

TB-500CellsNerve and immune cells: less damage and inflammationAnimalsAlzheimer’s-model mice: better memory tests; plaque unchangedPeople0 studiesFull-length thymosin beta-4Cells and animalsRat stroke: function improved; aged rats: no functional gainPeopleNone found

Safety

TB-500CellsSkin cells (fibroblasts): no cell damage seenAnimalsNo standard safety or cancer studies (FDA 2026)People0 studiesFull-length thymosin beta-4Cells and animalsCancer models mixed; high doses in pigs weakened clots with an antiplatelet drugPeopleIV in 124 healthy volunteers (2 studies): no serious adverse events

TB-500 in people: 0 studies (FDA 2026 review). Tiles show the type of evidence and the result in words, not strength of effect.

Every human trial used full-length thymosin beta-4, by other routes. The people column for TB-500 is empty.

What did the thymosin beta-4 trials find?

A company-affiliated review of the ulcer trials said thymosin beta-4 sped up healing "by almost a month" in the people whose wounds healed. That describes a subgroup of responders, not everyone treated. [101]

Why don't these trials tell us about TB-500?

Because almost everything about them is different. They used the whole 43-amino-acid protein rather than the capped 7-amino-acid fragment, applied it to the eye or skin surface or gave it into a vein rather than by subcutaneous injection, and studied eye disease, skin ulcers and heart attacks rather than tendons or joints. The IV doses also ran from micrograms per kilogram to over a gram a day, a scale that cannot be converted into a subcutaneous TB-500 dose. [1], [73], [86]

The FDA makes a related point about the fragment itself: results for an uncapped version cannot be carried over to capped TB-500, because the cap changes how a peptide behaves. Websites that describe these trials as "TB-500 trials" are borrowing evidence from a different molecule, and sometimes misreading it: "safe up to 1,260 mg a day" comes from the IV study of the full protein, and the often-quoted "25 mcg per kg daily for 10 days" was actually a single dose, with the 10-day doses going no higher than 5 mcg per kg. [1], [20], [65], [73], [86]

What would a useful improvement look like?

Pain, function and tissue structure are separate outcomes. One forum user with a partial rotator cuff tear, for example, slept without pain within two days but described being about 90% recovered only after eight months that included rehabilitation. [37]

Scans answer a different question again. In a forum post titled "MRI proof", a follow-up scan three months after a high ankle sprain showed healed ligaments after BPC-157, TB-500 and two months of physiotherapy; with no comparison, it cannot show what the peptides added. [102]

How might TB-500 work?

Healing a tendon or wound needs cells to move into the damaged area, new blood vessels to supply it, and inflammation to settle. In preclinical research (cell and animal studies), researchers link thymosin beta-4 to all three. The open question is how much of that the small TB-500 fragment keeps.

Thymosin beta-4 keeps actin building blocks in reserve

Actin is the protein that forms a cell's internal scaffolding. When a cell moves, it builds actin filaments at its front edge from single actin building blocks. Thymosin beta-4 binds those single blocks and keeps a reserve ready, which is thought to be essential for cell shape and movement. The first six amino acids of TB-500 (LKKTET) match the stretch of thymosin beta-4 that binds actin. [1], [103]

Injured muscle makes more thymosin beta-4, and in lab dishes it drew muscle precursor cells towards it. Whether actin binding explains the healing effects seen in animals has not been worked out. [104], [1]

Does the fragment do what the whole protein does?

Only partly, and the results conflict. [1]

• Uncapped fragment, mouse wounds: the 7-amino-acid sequence without the acetyl cap, applied to skin wounds in 26-month-old mice, improved wound closure about as well as the whole protein. A separate study also found it helped skin wounds in mice. [105], [106], [1]
• Capped TB-500, cells in a dish: in a scratch-wound test on connective-tissue cells (fibroblasts), TB-500 itself did not speed closure, while one of its breakdown products (Ac-LKKTE) produced a small effect. The authors suggest earlier reports of TB-500 activity may reflect that breakdown product. [82], [1]
• Other fragment findings: the same stretch blocked activation of human liver scar-forming cells in dishes; in mice bred to develop Alzheimer's-like disease, TB-500 and another thymosin beta-4 fragment (Ac-SDKP) reduced brain inflammation and improved memory tests, though amyloid plaque in the hippocampus did not change; a gel built from a modified peptide containing the TB-500 sequence helped burned corneas in an animal model; and injections of a product sold as TB-500, whose identity the study did not test, produced stronger repaired Achilles tendons in rats. [107], [108], [85], [38]

TB-500 also lacks parts of the whole protein that researchers link to other effects: the Ac-SDKP stretch at its start, studied for calming inflammation and scarring, and the first 15 amino acids, linked to cell survival. The FDA concluded that animal and lab evidence "is currently lacking" to show TB-500 promotes wound healing. [103], [1]

Does it grow new blood vessels?

In animal studies, thymosin beta-4 encourages angiogenesis, the growth of new blood vessels, and researchers map that activity to the region TB-500 copies. In pigs with narrowed heart arteries, gene delivery of thymosin beta-4 increased small connecting vessels and pumping strength, while in rats after a heart attack, repeated doses shrank the damage without increasing vessel density. [103], [109], [110]

New blood vessels are part of normal healing, but tumours also depend on them. That double edge is why the cancer question matters.

Where does the animal research fall short?

Enthusiastic summaries skip the results that did not work: thymosin beta-4 added regenerating muscle fibres without adding strength, shrank stroke damage in aged rats without improving function, failed to protect pig hearts, and worked less well at the highest dose in a rat stroke study. Almost all of this work used the full protein at milligrams per kilogram, doses that cannot be scaled into a human TB-500 dose. [41], [111], [12], [112] See the supporting research library for study-by-study detail.

What are the risks and unanswered questions?

Is TB-500 safe?

Its safety in people is unknown, because it has never been studied in people. The FDA found no human exposure data by any route and no standard animal safety studies: no single-dose or repeated-dose toxicity tests, no tests for DNA damage, no reproductive studies and no cancer studies. [1]

The FDA's main specific concern is the immune system. Injected peptides can trigger an immune reaction (immunogenicity), and clumps or impurities in a poorly characterised product can make that more likely; the FDA found nothing to suggest TB-500 is free of that risk. Two 2026 reviews of unregulated peptides warn more broadly about contamination, dosing errors and the potential for serious harm. [1], [88], [113]

The best reassurance available is borrowed: IV full-length thymosin beta-4 caused no serious adverse events in two short studies of healthy volunteers. Those studies used a different molecule, route and scale, and lasted two weeks at most, so they cannot show that injecting TB-500 for months is safe. [73], [86]

What side effects have been reported?

Official reports are almost empty, which reflects missing data more than proven safety. The FDA's adverse-event database had no reports mentioning TB-500 through March 2025, its food and supplement complaint system held two reports about "blended TB-500 and BPC-157" without safety details, and no case report has been published. In the FDA's separate BPC-157 review, one report of skin and gum darkening involved a product containing both peptides; it came back when the person restarted, but with two peptides the FDA could not tell which was responsible. [1], [114]

In the thymosin beta-4 trials, side effects were few: eye-drop discomfort, a serious episode of depression in one person in the corneal trial, and brief antibody detection with the IV version. [96], [98], [86]

Public forum reports, almost all from people also using BPC-157 or other peptides, describe tiredness or grogginess, sleep problems with evening doses, headaches, anxiety or a racing heart (in one case leading to an emergency visit with normal tests), flushing straight after injecting, allergy-type rashes and hives, and pain that returned each time a course was restarted. In community education groups, members describe similar short-lived problems, plus a whole-body hive-like reaction and two reactions that returned on restarting. None of these reports can establish how often an effect happens or what caused it; the experience section gives the details. [115], [80], [116], [62], [117], [37], [118], [119]

Could product quality change the risk?

Yes, and for TB-500 this is a documented, specific problem. What is sold under the name may be the fragment, full-length thymosin beta-4, a mislabelled amount or something else entirely. [1]

• In a 2026 preprint analysing a public database of consumer- and vendor-submitted tests of 14 gray-market peptides, TB-500 had the highest share of samples that did not contain the stated peptide (10%), the lowest median purity (97.3%), and the lowest share passing pharmacy-style standards for both purity and amount (22.5%). On the testing service's own page, many of the products tested are named "TB-500 (Thymosin Beta-4)". [10], [4]
• Years earlier, a US university racing laboratory found that many "TB-500" products sold for horses contained no thymosin beta-4 peptide at all, and most contained no protein or peptide of any kind. A 2023 analysis of internet products called TB500 and TB1000 found their contents did not consistently match their descriptions. [19], [120]
• One forum user paid for a laboratory test of a vial labelled 2 mg of thymosin beta-4 and found about 1 mg. [121]

In community education groups, members advise checking a certificate of analysis for the fragment's markers (such as "17-23" or a weight of about 889), while noting that it describes only the vials tested.

Is TB-500 legal? Is it FDA-approved?

Checked September 24, 2026. Rules differ by country and change quickly.

United States. TB-500 is not an FDA-approved drug and is not part of any approved drug. Its compounding status has several steps: [1]

• Earlier: a pharmacy nominated TB-500 (a 3 mg per mL injection for wound healing) for use in compounding, and it sat on the FDA's list of compounding ingredients that may present significant safety risks. The nomination was later withdrawn, and the FDA's safety-risk page now lists "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" as nominated but withdrawn. [1], [122], [123]
• May 2026: the FDA reviewed both forms on its own initiative and recommended against adding them to the list of substances pharmacies may compound, citing poor characterisation, no history of compounding use, no human safety or effectiveness data and the immune-reaction risk. [1]
• July 23, 2026: the FDA's Pharmacy Compounding Advisory Committee nonetheless voted 8 yes, 6 no and 1 abstention for each form. One member who voted no cited the overlap between thymosin beta-4 and tumour progression, and the lack of efficacy data. [124], [125], [126]
• Since then: the vote is advice, not a decision. As of September 24, 2026 no final FDA action or Federal Register notice has been published and no official minutes are posted, so US pharmacies may not compound TB-500 from bulk under the usual rules. Even if it is added later, compounded products would still not be FDA-approved. [127], [128], [126]

Canada. Health Canada's April 9, 2026 advisory lists TB-500 among examples of unauthorized injectable peptides it has seized, and warns that a "For Research Use Only" label does not make such products legal. [129]

Australia. TB-500 and thymosin beta-4 are each in Schedule 4 (prescription-only) of the June 2026 Poisons Standard, and on its list of substances that are illegal to possess without authority. [130]

New Zealand. Medsafe states that thymosin beta-4 and TB-500 are prescription medicines in New Zealand and Australia. [131]

United Kingdom and European Union. No product containing TB-500 is approved in the United Kingdom or authorised by the European Medicines Agency. We found no UK regulator statement that names it. [1]

A "research use only" label does not make a product legal to sell for human use.

Is TB-500 banned in sport? Does it show up on a drug test?

Yes, it is banned. The World Anti-Doping Agency's 2026 and 2027 lists name "Thymosin-ß4 and its derivatives e.g. TB-500" in category S2 (growth factors), prohibited in and out of competition. USADA added TB-500 as a named example in 2018. In US horse racing, the Racing Medication and Testing Consortium recommends treating it as a top-class prohibited substance. [13], [132], [133], [19]

Anti-doping laboratories have published methods to detect TB-500 and its breakdown products in urine, blood and dried blood spots. In rats, one breakdown product was still in urine 72 hours after a dose. How long it can be detected after use in people has not been published. [134], [135], [136], [82]

Does TB-500 cause cancer?

Nobody knows. There are no human data either way, and no animal cancer studies (carcinogenicity studies) of TB-500 have been done. [1]

The concern comes from the parent protein. In mice, melanoma cells making extra thymosin beta-4 grew into larger tumours with more blood vessels and far more lung spread; in colon cancer cells, extra thymosin beta-4 increased invasion, and switching it off reduced tumour growth from colon cancer stem cells. Thymosin beta-4 and three of its fragments also made ovarian cancer cells move and multiply faster in dishes; none of the fragments was TB-500 itself, though one contained its sequence within a longer piece. On the other side, added thymosin beta-4 slowed lung cancer growth in one mouse model. [11], [137], [138], [139], [140], [141]

So the concern is theoretical but taken seriously: it was one of the reasons given for a "no" vote at the FDA advisory committee. We found no published case report linking TB-500 to cancer, which reflects the absence of monitoring as much as anything. In community education groups, members with a history of cancer describe avoiding TB-500 or waiting for pathology results before considering it. [124]

Who should be especially cautious?

These groups have no safety data. That is a reason for caution, not proof of harm. [1]

• Pregnancy, trying to conceive and breastfeeding. No reproductive studies exist in any species.
• A current or past cancer. See the cancer question above.
• Under 18. No studies include young people. This guide is written for adults.
• Upcoming surgery, bleeding disorders or blood-thinning medicines. Nothing is known about bleeding or clotting in people, and one pig study found that high doses of thymosin beta-4 weakened clots when combined with an antiplatelet drug in the lab. Tell your surgeon and anaesthetist about everything you take. [12]
• A history of allergic reactions or hives. Allergy-type reactions are among the reported problems, and immune reactions are the FDA's main specific concern.
• People prone to anxiety, panic or palpitations. These are among the more frequent public reports, though cause is unproven.
• Competitive athletes. It is banned in and out of competition. [13]
• People taking other medicines. Interactions have not been studied; see the next question.

Has TB-500 been tested alongside other medicines?

No. There are no interaction studies. In a 2026 analysis of US clinical notes (a preprint), TB-500 was documented in 12.9% of people recorded as using BPC-157, and testosterone and anti-inflammatory painkillers (NSAIDs) were other common companions; in public forums, people add it to testosterone, anabolic steroids, growth hormone and weight-loss medicines. None of these combinations has been studied. Bring a complete list of everything you take to a pharmacist or doctor. [34], [48], [33], [31]

What should be monitored while using TB-500?

There is no official monitoring guidance, because no regulator has approved TB-500 or written a label for it. What can be described is what the human studies of full-length thymosin beta-4 measured, and which checks follow from the concerns in this guide. It is information to discuss with a clinician, not a personal testing plan. [1]

The IV thymosin beta-4 safety study tracked blood chemistry (including liver and kidney markers), blood counts, urine tests, heart tracings (ECG), heart-injury and clotting markers, blood fats, tumour markers and antibodies against the drug. A marker called SCC rose briefly in both the drug and placebo groups and returned to normal. The venous-ulcer trial checked blood chemistry, blood counts, clotting and urine every week. [86], [142]

None of these checks makes an untested compound safe. They show what is changing, which is what a clinician needs to judge whether to continue.

What do people in public communities report?

Public discussions contain quick recoveries, slow partial ones, no change at all, and symptoms that made people stop. Almost every account involves TB-500 alongside BPC-157, often with other peptides, testosterone or steroids, physiotherapy and rest, and many people cannot be sure which molecule their vial contained. The most useful accounts explain what else was happening and come back with an update. [32], [63], [143]

What do the positive reports look like?

Older forum threads include some of the few TB-500-only accounts. One person on testosterone, doing physiotherapy stretches, injected 2.5 mg into a muscle twice a week: biceps tendinitis was nearly gone in two weeks and shoulder impingement improved, but arthritis in the shoulder joint did not change. Another used 5 mg a week for four weeks, then 2 mg a week for two, and described plantar fasciitis, forearm tendinitis and a rotator cuff strain all resolving. [32], [37]

Recent accounts are mostly blends. A person with long-standing pain in both knees took 500 mcg each of BPC-157 and TB-500 on weekdays for five weeks, noticed a slight change in the first two weeks, felt about 95% better by week three, and later said the pain had not returned months after stopping. Another took 1 mg of BPC-157 and 0.5 mg of TB-500 daily for Achilles tendinitis and was running again by week three, after an early dip in strength. [80], [36]

The follow-ups matter. A widely shared "40 days" knee recovery also involved 40 days of complete rest from running and leg training, and the poster later said the vial was full-length thymosin beta-4. A partial patellar tendon rupture that returned to sport by month five also involved platelet-rich plasma injections, an anabolic steroid, bracing and a structured rehabilitation plan. [143], [144]

Members of community education groups also describe improvement, mostly for shoulders, elbows, knees and Achilles tendons, sometimes within days.

How quickly did people notice anything, and did it last?

Many of the positive accounts we reviewed describe a change within days to three weeks; others describe slow progress over months. A few describe pain vanishing within minutes of a local injection, which fits expectation better than tissue repair. [43], [37], [81]

Some people's pain came back soon after stopping, while others stayed well for months. See what happens when people stop. These accounts cannot provide an average time to benefit: they involve different injuries, products and combinations, and the people posting are not a representative sample of everyone who has tried TB-500.

Does everyone notice a difference?

No. Many of the accounts we reviewed describe no benefit, especially for long-standing structural problems and for injuries that people kept loading. [87], [43], [44]

• Tennis elbow while still training: six weeks of BPC-157 twice daily plus TB-500 1.5 mg three times a week brought no improvement at all. [87]
• Hip labral tears: eight weeks of 2.5 mg twice a week, half of it injected near the hip, changed nothing, and the person was waiting for surgery. Another person with two years of hip and knee pain used third-party-tested BPC-157 and TB-500 at high amounts and had only a slight improvement that did not last. [43], [44]
• Chronic shoulder pain: three months, including doubling the TB-500 amount, did nothing. [32]
• A prescribed course: a doctor-prescribed, compounded thymosin beta-4 and BPC-157 course costing about AUD 1,500, with the amounts doubled halfway through, "helped a bit but less than expected" for three years of wrist inflammation. [63]

Members of community education groups describe the same pattern: severe arthritis and full tears that did not improve or went to surgery anyway, and some people who noticed nothing even at high amounts.

Does getting worse mean it is working?

The reviewed accounts do not support that idea. A few people describe more soreness or injection-site sensitivity at the start, but nothing shows that a flare is a sign of healing. In community education groups, one member's worsening in the first week came with several compounds started at once. Describing it as a necessary "healing phase" adds an explanation the accounts cannot establish. [79]

What about unwanted effects?

The detailed accounts are worth reading as stories, not statistics. [117], [62], [145], [146], [119], [147]

• Panic and a racing heart: a person prescribed compounded thymosin beta-4 at about 500 mcg a day developed panic, adrenaline surges and a raised heart rate within days, stopped on day six, and went to an emergency department, where blood tests, an X-ray and an ECG were normal; the symptoms took more than a month to settle.
• Fainting: another person reported dizziness and briefly losing consciousness straight after a first 2.5 mg injection. The cause was never established (the poster later guessed at a faint or a panic attack), and they reported no problem when they tried again.
• Emotional numbness: a single 500 mcg clinic dose was followed by emotional blunting and heavy brain fog for a few days.
• Pain that returned on restarting: one person had a dull pain in the same area on two separate courses from two suppliers; it went away after stopping each time.
• Drowsiness: one person stopped a BPC-157 and TB-500 combination because of unbearable drowsiness, then used TB-500 alone without it.

When people using blends describe injection-site pain or welts, the public posts we reviewed blame GHK-Cu rather than TB-500, while others on the same blends report no problem; community education groups describe the same pattern. Posts like these cannot establish the cause. [35], [148] The risks section covers what the FDA found.

How can you judge a recovery story?

Useful questions to ask: What was the starting problem, and how long had it lasted? What exactly was used, how much, and was the vial ever tested? What else changed, such as rest, physiotherapy, surgery or other drugs? What happened weeks or months later? [149]

Separate pain relief from restored function and confirmed tissue repair, and remember that many injuries improve with time and rest. These selected discussions help identify experiences that research should examine. They are not a survey of all users, a response-rate estimate or a substitute for controlled human studies.

How does TB-500 compare with thymosin beta-4, BPC-157, thymosin alpha-1 and GHK-Cu?

These are the peptides TB-500 is most often combined with or confused with. No study has compared any of them directly with TB-500, so the table compares what each one is and how much human evidence exists. The route and schedule column describes what protocol sources or labels say, not tested doses for TB-500 or BPC-157.

The real differences are in identity and evidence, not in proven results. Thymosin beta-4 is the full protein TB-500 is copied from and has human trials where TB-500 has none, though none of them tested injections for injuries (see the full comparison). TB-500 and BPC-157 are the two halves of the Wolverine stack, but BPC-157 has three small human reports of its own and TB-500 has none. Thymosin alpha-1 shares only part of a name: it is a different molecule with a different job, and it is the only one of these with an approved medicine in any country we checked. KLOW and GLOW add GHK-Cu (and, in KLOW, KPV) to BPC-157 and TB-500; no study has tested these peptides together or against each other in people.

Common questions about TB-500

How long does TB-500 take to work?

Nobody can say, because no study has measured it. Public accounts range from a change within days, through steady improvement over two or three months, to no change at all, and most involve BPC-157, rest or rehabilitation at the same time. [80], [37], [87]

It also matters what "working" means: less pain at rest, getting through training, and a healed tendon on a scan are separate milestones, and they do not arrive together. See what people reported over time.

Is TB-500 the same as TB4, TB-1000 or thymosin alpha-1?

No. TB4 usually means full-length thymosin beta-4, the 43-amino-acid protein that TB-500 is a small piece of, and the two are often sold under the same name. "TB-1000" is another internet product name; a 2023 laboratory analysis found that products called TB500 and TB1000 did not consistently contain what they claimed. Thymosin alpha-1 is an unrelated immune peptide that shares only the word "thymosin". [1], [120], [154] See how TB-500 differs from thymosin beta-4.

What is the Wolverine stack, and why is TB-500 taken with BPC-157?

The Wolverine stack is BPC-157 and TB-500 used together, either from separate vials or a pre-mixed vial. Protocol pages describe the two as working in complementary ways, but no study in people has tested the combination, and in the one rat study that compared them, the pair gave no added benefit over either product alone. Combining them also means you cannot tell which peptide helped or caused a side effect, and a pre-mixed vial's label gives the total of both. [65], [28], [38] See the blend table, and read the Doserly guides to BPC-157 and the Wolverine blend.

Can TB-500 be taken by mouth or as a nasal spray?

Neither has been tested in any species. Laboratory work shows TB-500 is readily broken down by human enzymes, and short peptides generally do not survive digestion intact, so a capsule is unlikely to deliver it the way an injection does. All the protocols compared in this guide are injections. [84], [83] See why the route matters.

Is TB-500 a steroid or a growth hormone?

No. TB-500 is a short peptide, not a steroid (steroids are built on a ring-shaped core and act on hormone receptors) and not growth hormone. Anti-doping rules place it among growth factors, alongside substances such as IGF-1, and ban it at all times. That classification says nothing about whether it works or is safe. [13], [1]

Is there an FDA-approved TB-500 dose?

No. TB-500 is not part of any FDA-approved drug, has no label, and no dose has been tested in people. The amounts in this guide come from protocol websites. [1] See typical protocols and where they differ.

Is it legal to buy TB-500?

It depends on where you live. It is not FDA-approved or legal to compound from bulk in the United States, Health Canada lists it among seized unauthorized peptides, and it is prescription-only in Australia (where possessing it without authority is illegal) and New Zealand. A "research use only" label does not make a product legal or safe to use. [1], [129], [130], [131] See the dated legal-status summary.

Is a higher dose or a longer course more likely to work?

The available evidence cannot say. Published amounts vary about tenfold, and public accounts include people who raised the amount or kept going for months with no benefit, as well as people who improved on small daily amounts. Higher and longer use also raises safety questions that no study has answered. [8], [32], [44], [1]

Glossary

Plain explanations of the route, dosing, research and regulatory terms used in this guide. Underlined terms in the text link here.

Acetylation (acetyl cap)

Adding a small chemical cap called an acetyl group to a molecule. TB-500 carries one on its first amino acid, which changes how it behaves compared with the uncapped sequence.

Actin

A protein that forms the filaments of a cell's internal scaffolding. Cells build and dismantle actin filaments to change shape and move.

Adverse event

A harmful or unwanted medical event reported after someone used a treatment. A report alone does not prove the treatment caused it.

Advisory committee

A panel of outside experts that gives the FDA advice. Its votes are not binding; the FDA makes the final decision.

Aggregation

Peptide molecules clumping together. Clumps can make a product weaker and, when injected, more likely to trigger an immune reaction.

Amino acid

A small chemical building block. Chains of amino acids make up peptides and proteins.

Angiogenesis

The growth of new blood vessels from existing ones. It is a normal part of healing, and researchers also study it closely in cancer.

Animal study

Research in animals such as rats or mice. It shows what a substance does in a living body, but results in people can differ.

Bioavailability

How much of a dose reaches the bloodstream in a usable form. It depends heavily on the route.

Blend

A product that combines two or more peptides in one vial, such as TB-500 with BPC-157. The blend's total amount is not its TB-500 amount.

Carcinogenicity study

A long-term animal study designed to detect whether a substance can cause cancer. None has been done for TB-500.

Cell study (in vitro)

Research on cells grown in a dish. It gives early clues about biology, but it is far from proof of benefit in people.

Certificate of analysis

A supplier's report of laboratory tests on a product, such as identity and purity. It describes the samples tested, not every vial, and may leave out important tests.

Compounding

When a pharmacy prepares a customized medicine from individual ingredients. In the US, federal lists control which bulk ingredients pharmacies may use.

Controlled trial

A study that compares people who receive a treatment with a similar group who do not, often receiving a placebo instead. Randomly assigning people to each group makes the comparison fairer.

Course and cycle

A course is the period of repeated use, such as six weeks. A cycle is a course plus a planned break before any further use.

Daily total

All the amounts given in one day, added together. For example, 250 mcg twice daily is a 500 mcg daily total.

Dose (amount each time)

The amount given on one occasion. A protocol lists both the dose and how often it is given.

Fibroblast

A cell that builds and maintains connective tissue, such as tendon, mainly by making collagen.

Freeze-dried (lyophilized)

Dried by freezing and removing the water, leaving a powder. TB-500 is sold this way and mixed with liquid before injection.

Half-life

The time it takes for the measured level of a substance in the blood to fall by half. It is not the same as how long an effect lasts.

Immunogenicity

The tendency of a substance to provoke an immune response, such as antibodies or an allergic reaction. It is the FDA's main specific concern for injected peptides like TB-500.

Intramuscular (IM)

Injected into a muscle.

Intravenous (IV)

Given directly into a vein, so it enters the bloodstream immediately.

Investigational

Still being studied and not approved by a regulator, such as the FDA, to treat any condition.

Loading phase

Starting with a higher amount or more frequent doses for a period, then lowering it. TB-500 protocols usually load for 4–6 weeks.

Maintenance phase

The less frequent phase that follows loading, such as one injection a week, used to continue a course at a lower level.

mcg and mg

Micrograms and milligrams. 1 mg equals 1,000 mcg. Twice-weekly TB-500 amounts are usually written in mg; daily and blend amounts are often in mcg.

Metabolite (breakdown product)

A smaller molecule the body makes when it breaks a substance down. TB-500 is cut into several shorter pieces, some of which last longer than TB-500 itself.

Micromole

A way of counting molecules rather than weighing them. Because thymosin beta-4 is about 5.6 times heavier than TB-500, the same number of milligrams contains about 5.6 times fewer molecules.

Oral

Taken by mouth, as a capsule, tablet or liquid.

Peptide

A short chain of amino acids. TB-500 is a chain of 7; thymosin beta-4 is a chain of 43.

Pharmacokinetics

How the body absorbs, moves, breaks down and removes a substance.

Phase 1, 2 and 3 trials

Clinical trials run in stages. Phase 1 checks safety in small groups, phase 2 looks for effects and doses, and phase 3 tests benefit in larger groups.

Placebo

A dummy treatment with no active ingredient, used as a comparison in studies.

Preclinical research

Studies done before research in people: cell studies and animal studies.

Primary endpoint

The main result a trial is designed to measure. Missing it means the trial did not show the benefit it set out to test.

Reconstitution

Mixing a freeze-dried powder with a liquid so it can be measured and injected. The amount of liquid sets how much peptide each unit holds.

Research use only

A label on products sold for laboratory research. It does not mean a product is approved, tested for human use or legal to sell as a medicine.

Schedule 4 (Australia)

Australia's prescription-only medicine category. TB-500 and thymosin beta-4 are both listed there.

Subcutaneous (SC)

Injected into the fatty layer just under the skin. This is the route most TB-500 protocol descriptions use.

Syringe units

Markings on an insulin syringe that measure volume. On a U-100 syringe, 100 units equal 1 mL. The amount of drug per unit depends on the vial's concentration.

Thymosin beta-4 (TB4)

A 43-amino-acid protein made by most of the body's cells that holds actin building blocks in reserve. TB-500 copies 7 of its amino acids, and many products sold as TB-500 contain the whole protein.

Titration

Adjusting a dose in steps, usually starting lower and increasing if needed.

Trial registry

A public database, such as ClinicalTrials.gov, where studies are recorded before they run. A registration is a plan, not a result.

WADA

The World Anti-Doping Agency, which publishes the list of substances banned in sport.

Weekly total

All the amounts given in one week, added together. For example, 2.5 mg twice a week is a 5 mg weekly total, and 500 mcg daily is 3.5 mg.

Withdrawal and rebound

Withdrawal effects are symptoms caused by stopping a substance. A rebound is a problem returning worse than before after stopping. Neither has been studied for TB-500.

Explore more of the research

Go deeper into the experiments behind the claims. Most of them studied full-length thymosin beta-4, not TB-500; each entry says which molecule was used.

Across this guide, the citations include 63 original scientific papers (49 cell, animal and laboratory papers and 14 human studies, none of which gave anyone TB-500), plus 3 preprints that have not yet been peer reviewed. The optional library below explores 49 of the laboratory and animal papers, grouped by question. Paper counts are not counts of independent research teams: several come from the same groups. Registry plans, reviews, regulatory documents, websites and personal accounts are counted separately.

In the route details, intraperitoneal means into the abdominal cavity; intradermal, into the skin; and topical, applied to the surface.

How this guide was researched

This guide is built from a thorough review of the sources cited throughout it: published scientific studies, registered clinical-trial plans, regulatory documents, anti-doping and product-testing research, and published protocol descriptions. We also reviewed public online forums and community education groups where people describe their own experiences with TB-500.

The guide cites 180 sources, including 63 original scientific papers. Each type of source answers a different question. Studies show what researchers measured. Protocol descriptions show how TB-500 is typically used. Personal accounts show what individual people experienced. Every numbered citation links to its entry below, labeled by source type.

How this guide was made

Research and drafting were AI-assisted. Every cited source was checked against the original, and the guide was reviewed and edited by Doserly before publication. It has not had an independent clinical review, and Doserly does not currently have medical reviewers. Doserly makes a medication and health-tracking app and runs Doserly Academy, both of which are promoted in this guide. Read our editorial policy for how guides are researched, updated and corrected.

This guide is for educational purposes. It summarizes what the reviewed sources report so the research is easier to understand; it is not medical advice. For a deeper dive, or to check any point for yourself, go straight to the cited sources.

Explore the sources