Testosterone Undecanoate Injection: The Definitive Guide

What is testosterone undecanoate injection?

Testosterone undecanoate injection is a prescription form of testosterone that lasts for months. It is testosterone with a long chemical tail attached, dissolved in castor oil and injected deep into the buttock muscle by a nurse or doctor. One injection keeps levels up for about 10 to 14 weeks, so most men need 4 or 5 injections a year once treatment settles. [1], [2]

"Undecanoate" is an 11-carbon ester (a chemical tail) joined to testosterone. The long tail makes the hormone leave the oil very slowly; the body then clips it off to release ordinary testosterone. Because the tail adds weight, a 1000 mg dose contains 631.5 mg of testosterone. [1], [2]

It is labeled for adult men with hypogonadism (low testosterone from a medical cause): primary hypogonadism, where the testicles fail, or hypogonadotropic hypogonadism, where the brain and pituitary do not send enough signal. The US label says its safety and benefit in "age-related" low testosterone, and in anyone under 18, have not been established. [1]

[1], [2], [3], [4], [5], [6], [7], [8]

Every product is 250 mg/mL in castor oil with benzyl benzoate. No injectable form is sold in Canada, and Aveed is the only version approved in the United States (checked September 2026). [1], [2], [9], [10]

It is not the same as oral testosterone undecanoate. Jatenzo, Kyzatrex, Tlando and the older Andriol capsules contain the same ester but are swallowed with food twice a day and absorbed through the gut's lymph vessels. They are different products with different doses; see oral testosterone. [11]

Testosterone undecanoate is a controlled substance: Schedule III in the United States. Unlicensed vials sold outside medical care are not covered by the labels described here, and doses above the natural range are not testosterone replacement therapy, or TRT (see TRT vs steroids). [12]

Typical Testosterone Undecanoate Injection Protocols

The US and UK labels and the guidelines above use one whole vial per injection and change only the gap between injections: Aveed every 10 weeks after a second dose at 4 weeks, and the 1000 mg products every 10 to 14 weeks, most often about every 12 weeks. The Australian labels also allow a smaller volume when levels run high. [1], [2], [4], [15], [16], [17]

Titration Adjusting the schedule in steps

Aveed's label keeps the dose and the 10-week interval fixed; the AUA guideline allows 9 or 11 weeks by the end-of-cycle trough. The 1000 mg labels and non-US guidelines mainly adjust the interval, using the testosterone level just before the next injection: a low trough shortens the gap and a high one lengthens it. The Australian labels also allow a smaller volume when levels are high, without giving an amount. The sources differ on when to check first and on the target. [2], [4], [14], [15], [16], [17], [18] See when blood should be drawn.

Breaks and cycles

Not applicable. Testosterone replacement is continuous treatment; no label or guideline describes planned breaks or cycles. Stopping is a separate decision, and the depot keeps releasing testosterone for months after the last injection (what happens when you stop). [17]

Read the units. Doses are written in milligrams (mg), and every product is 250 mg/mL, so 750 mg is 3 mL (the whole Aveed vial) and 1000 mg is 4 mL (the whole Nebido ampoule or vial). Insulin-syringe units do not apply: the volume is far more than a 1 mL syringe holds, and the labels use the full single-use container (the Australian labels also allow a smaller volume when levels are high). The weekly figures in the table are averages for comparing with weekly injections, not doses anyone gives: 750 mg every 10 weeks averages 75 mg a week. For shorter-acting injections, where you draw part of a vial, Doserly's TRT dose calculator does the mg-to-mL arithmetic. [1], [2]

These are labeled and guideline doses; prescribers adjust them using blood tests and symptoms. The schedules above are for adult men. For women, see testosterone therapy for women, which uses different products and far smaller doses.

Cautions for every schedule above. The labels rule out testosterone with breast or prostate cancer, pregnancy and allergy to the ingredients, including castor oil or benzyl benzoate; the UK label adds liver tumors. Every injection carries a small risk of an oil cough or allergic reaction (POME), testosterone shuts down sperm production (fertility), and hematocrit, blood pressure and PSA (prostate-specific antigen, a prostate blood test) need checking (monitoring). [1], [2]

Where schedules differ: fixed or adjusted intervals, the loading dose, wearing off, blood-test timing and splitting the vial ↓

What do clinic protocol sources use?

About 70% of men in that clinic ended on an interval between 10 and 14 weeks after adjustment, with a median of 12.0 weeks. The clinic also treated transgender men, so its numbers are not limited to men with hypogonadism. [19]

What is testosterone undecanoate injection commonly used for?

Its approved use is replacing testosterone in adult men whose bodies cannot make enough because of testicular failure or a missing signal from the brain or pituitary, when the benefit outweighs the risk of the injection reactions described below. [1], [20]

Is it a good first choice? Guidelines disagree. The BSSM and the Australian statement list convenience and steadier levels as advantages; at 10 to 14 week gaps that is about 4 or 5 injections a year. But it cannot be self-injected or stopped quickly once given, so the Society for Endocrinology does not recommend it first-line, and the EAU prefers a gel when starting treatment in men at higher risk. [16], [18], [17], [15]

What does testosterone replacement improve?

Mainly sexual desire and function in men with clearly low levels. Trials of undecanoate injections show that pattern:

• Men with type 2 diabetes (BLAST). In 199 men randomized to undecanoate injections or placebo for 30 weeks, erectile function improved only in men with severe deficiency (total testosterone 8 nmol/L or lower, about 230 ng/dL, with low free testosterone) and only by week 30. Desire and satisfaction improved from week 6 in that group. [21]
• Men with prediabetes (T4DM). Over 2 years, 10 more men in every 100 had a meaningful gain in sexual desire than on placebo (32% vs 22%); the difference in erectile function, 3 more in 100, was not significant. [22]
• Men with low libido on a daily gel (TRAVERSE). In 1,161 men, testosterone gave more sexual activity and desire through 24 months but did not improve erections. This trial tested a gel, not injections. [23]
• Compared with enanthate. In a German trial of 40 men, sexual function improved as much on undecanoate as on enanthate over 30 weeks and stayed improved for 65 more weeks. [24]

Body composition shifts too. In T4DM, where every man was in a lifestyle program, fat mass fell 4.6 kg on testosterone vs 1.9 kg on placebo over 2 years. In obese men on a very low energy diet, undecanoate injections led to 2.9 kg more fat loss and 3.4 kg less lean-mass loss than placebo over 56 weeks. [25], [26] See the evidence and the muscle and fat loss guide.

Does it prevent diabetes?

Not on its own. In T4DM, 1,007 men aged 50 to 74 with a large waist and prediabetes or newly diagnosed diabetes all joined a lifestyle program, and half also received 1000 mg undecanoate injections. At 2 years, 12% of the testosterone group (55 of 443) had diabetes, compared with 21% on placebo (87 of 413). [27]

TRAVERSE, which used a daily gel without a structured lifestyle program, found no significant diabetes prevention, and the American Diabetes Association does not recommend testosterone to prevent type 2 diabetes. The T4DM result also came with more high hematocrit (below). [28], [29]

How long does testosterone undecanoate injection take to work?

Blood levels rise from the first day, but effects take weeks. After an Aveed injection, levels peak at a median of 7 days and reach a steady state with the third injection at week 14; on Nebido every 10 weeks, between the third and fifth injections. [1], [2]

A German study of 40 men on undecanoate or enanthate timed each effect. Sexual interest and morning erections improved quickly and leveled off after 3 weeks, erections after 9 weeks, and sexual satisfaction after 12. Depression scores leveled off after 6 weeks and fatigue improved after 9 to 12 weeks. Concentration took 9 weeks on undecanoate compared with 3 on enanthate. [30] See the results timeline guide.

Where do testosterone undecanoate protocols differ?

The dose is one vial on the US and UK labels, and the Australian labels also allow a smaller volume when levels run high. The main disagreements are about timing: the second injection, the gap, blood tests and splitting the vial.

Fixed every 10 weeks, or adjusted between 10 and 14?

The US and the rest of the world run the same drug on different rules. Aveed's label gives 750 mg every 10 weeks after a 4-week second dose and says titration is not necessary. For the same regimen, the AUA guideline allows a 9-week gap if the trough at the end of a cycle is under 300 ng/dL (about 10.4 nmol/L) and an 11-week gap if it is over 600 ng/dL (about 20.8 nmol/L). The 1000 mg labels in the UK and Australia let the interval move between 10 and 14 weeks, set by the testosterone level at the end of each interval, and the Australian labels also allow a smaller volume when levels are high, without giving an amount. [1], [14], [2], [4]

In practice, the adjusted schedules tend to settle near 12 weeks. In the Sydney clinic, 23% of men ended on 14 weeks or longer and 7.4% on 10 weeks or shorter. Early studies that kept injecting every 6 weeks found peaks and troughs creeping upward with each injection, and the Australian label says that interval caused testosterone to build up, so a longer gap was needed. [19], [31], [4]

Is the second injection at 4 or 6 weeks a loading dose?

Yes. The early second injection, a loading dose, brings levels to a steady pattern sooner. Aveed builds it in at 4 weeks. The 1000 mg labels allow the first interval to be shortened to a minimum of 6 weeks as an option, not a requirement, while UK and European guidelines routinely give it at 6 weeks (6 to 8 in the Society for Endocrinology guideline), with the third injection 12 weeks later. On Nebido, that second injection produced the highest peak, about 50 nmol/L (about 1,440 ng/dL), before levels settled. [1], [2], [4], [15], [16], [17]

Doserly

The first year on each labeled schedule

Weeks 0 to 52, drawn to scale. Dots are injections; a dashed ring is an optional early injection; amber diamonds are trough blood tests; a dashed line is a mid-interval test.

Aveed (US label): 6 injections in year 1

750 mg (3 mL) each at weeks 0, 4, 14, 24, 34 and 44. The label is fixed, with no titration; 30 minutes’ observation after each. The AUA’s first check falls halfway between the first two 10-week injections (week 19), a mid-interval level, not a trough; the AUA also allows a 9 or 11 week gap, set by the trough at the end of a 10-week cycle.

1000 mg products (UK, Australia): 5 injections in year 1

1000 mg (4 mL) each at weeks 0, 6 (optional early second injection), 18, 30 and 42: every 12 weeks shown, within the labeled 10–14, with the interval set by the trough. BSSM and the Society for Endocrinology draw the trough before the 3rd injection (week 18). The Endocrine Society of Australia gives injections every 3 months from the start, so its trough before the 4th injection falls at about week 39, not on this track.

Injection timing is arithmetic from the labels; it is not a level curve. EAU checks the trough after 3–5 injections.

Why do some men feel it wear off before the next injection?

It is the most common complaint in public forums, and no study has measured how often it happens. On Aveed at steady state, the average lowest level just before the next injection was 324 ng/dL (about 11.2 nmol/L), with wide variation between men. The Nebido label reports that the trough varied by 22% within the same man and 34% between men. [1], [2]

Body size matters. On the Aveed label, men weighing 100 kg or more averaged 426 ng/dL across the interval, compared with 568 ng/dL in men weighing 65 to 100 kg. [1]

One clinic shortened intervals only when a man's own symptoms returned early and his trough was low; 7.4% ended on 10 weeks or less. A computer model by authors linked to Aveed's maker predicted that every 8 weeks instead of 10 would keep the trough above 300 ng/dL in 76.1% of simulated men instead of 66.7%; that is a simulation, and 8 weeks is not in the label. [19], [32]

Late-interval symptoms have other causes too, such as poor sleep, weight change or other medicines; a trough drawn just before the next injection shows whether the level really is low. See what people describe in the community section.

When should blood be drawn?

Just before the next injection, according to the labels and most guidelines, but the first check and the target differ. A result from the middle of the interval looks higher than one from the end, so a mid-interval level cannot be judged against a trough target. [2], [13], [14]

[2], [13], [15], [16], [17], [18], [14]

The Nebido label also asks for every testosterone test to be done at the same laboratory, because results vary between labs. [2] See TRT blood work for the full picture.

Can the vial be split into smaller, more frequent doses?

Not established. No published study has tested dividing a castor-oil undecanoate vial into weekly or two-weekly doses, and no label or guideline describes dividing a vial that way. The Australian labels do allow a smaller volume when levels are high, but they give no amount and treat each container as single use. The labels treat each ampoule or vial as a single use: the Nebido label says to inject it immediately after opening and discard any leftover, and Aveed's vial is single use. [2], [1], [4]

Splitting is still widely discussed, and some prescribers outside the labels have tried it (what people report). The labels give no in-use period once a container is opened. If the aim is weekly dosing, the labeled options are cypionate or enanthate, which come in multi-dose vials; see testosterone cypionate and testosterone enanthate.

Can it be injected subcutaneously?

Only in one small study. In a randomized crossover study of 20 long-term users (11 men with hypogonadism and 9 transgender men), a full 1000 mg dose injected subcutaneously (into the fatty layer under the skin) gave testosterone, dihydrotestosterone (DHT) and estradiol levels similar to an injection into muscle, with a later peak (8.0 vs 3.3 days). It was more painful 24 hours later, and 11 of the 20 preferred the muscle injection. The labels allow intramuscular use only. [33], [1], [2]

How do people switch from cypionate or enanthate?

There is no fixed rule, and the only trial schedule comes from one German study. Men moving from enanthate 250 mg every 3 weeks received two 1000 mg undecanoate injections 8 weeks apart, then one every 12 weeks. In the same trial, enanthate troughs were always below 10 nmol/L before the next injection, while undecanoate troughs averaged 14.1 nmol/L after the first two doses and 16.3 nmol/L after the first 9-week interval. [34]

No guideline sets a gap between the two products, so ask the prescriber whether the first undecanoate injection replaces your next due short-ester injection and when to draw the first trough. Switching back to a short ester raises the same question in reverse, because undecanoate clears slowly (stopping). [2]

What happens when you stop testosterone undecanoate injection?

The drug leaves slowly, and your own hormone production returns even more slowly. [2], [35]

• After the last injection. Levels fall over months, because the depot keeps releasing testosterone (release half-life 90 ± 40 days on the Nebido label). [2]
• Your own testosterone. Injected testosterone switches off the pituitary's signals to the testicles, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In T4DM, in men who did not have a medical cause of low testosterone, LH and FSH recovered slowly over 12 months after 2 years of 1000 mg injections, and full recovery may take longer. For men with a verified diagnosis of hypogonadism, the Society for Endocrinology expects treatment to continue lifelong. [35], [17]
• Sperm. In a small series of 8 men in couples trying to conceive who had been given Nebido, sperm disappeared after a median of 8 months, and sperm counts and FSH returned to normal a median of 8.5 months (range 7 to 10) after stopping. [36]
• Restarting. About five years after T4DM ended, 6% of men from the testosterone group had restarted testosterone, compared with 2.8% from the placebo group. [37]

See stopping TRT for the full picture, including fertility recovery and what men describe.

How long does testosterone undecanoate injection last, and how is it given?

It is the longest-acting testosterone injection. Compared with cypionate or enanthate, it needs 4 or 5 injections a year instead of 13 to 52, gives smoother levels between injections and, in a network meta-analysis, raised hematocrit less. In exchange, it must be given in a clinic, it cannot be removed once injected, and it carries the injection-reaction warning. [1], [34], [38]

How long does testosterone undecanoate last in the body?

Much longer than any other injectable ester, but published half-life figures differ by source and method, so each needs its label:

[2], [4], [39], [15]

These figures describe the depot; testosterone itself is cleared from the blood within minutes to about an hour. The "34 days" often repeated online comes from a single injection, not repeated dosing. [1], [39]

What do the levels look like between injections?

Smoother than on short-acting injections, but not flat:

[1], [2]

On Aveed, 94% of men kept an average level within 300 to 1,000 ng/dL (5.1% below, 0.9% above), and 7.7% peaked above 1,500 ng/dL, none above 1,800. [1] Doserly's testosterone level visualizer sketches a simplified undecanoate curve next to other esters.

Aveed (United States)

Aveed is testosterone undecanoate 750 mg in a 3 mL single-use vial, given only through a restricted safety program. FDA approved it on March 5, 2014, after an application first filed in August 2007 was turned back three times (an approvable letter in 2008 and complete response letters in 2009 and 2013), largely over the oil-cough and allergic reactions. [40], [41]

• The restricted program (REMS). Under FDA's Risk Evaluation and Mitigation Strategy (REMS), prescribers train, pass a knowledge test and enroll, and every clinic giving Aveed must be certified, keep equipment and trained staff on site for severe reactions, and watch each patient for 30 minutes after every injection. The current document dates from October 2024. [42], [43]
• Only one US version. A generic 750 mg/3 mL undecanoate injection from Hikma has had tentative approval since December 9, 2016, but no final approval, so Aveed remains the only approved US product (checked September 2026). [10]
• Label changes. A July 2025 update removed the old "Cardiovascular Risk" warning section and added blood-pressure warnings and TRAVERSE results, following FDA's February 2025 class-wide letter. This was a warnings section, not the boxed warning, which is unchanged. [44], [1]
• Why 750 mg, not 1000 mg. No 1000 mg product such as Nebido has US approval; Aveed's approval rests on studies of its own 750 mg schedule. [10], [45], [46]

Nebido and other 1000 mg brands

Nebido is testosterone undecanoate 1000 mg in a 4 mL ampoule or vial, first authorized in the UK on October 20, 2004. Its UK license holder is now Grünenthal; a 2014 review dates the injection to 2003. [2], [47]

The same 1000 mg/4 mL product is sold under other names: Roxadin in the UK; Reandron 1000, Rejunon 1000 and Gonadron in Australia, where the PBS also lists a Testosterone ADVZ 1000 brand; and generics in France and Spain. Their labels share the 10 to 14 week schedule. [3], [4], [5], [6], [48], [7], [8]

Outside the US there is no REMS. The Nebido label asks for the patient to be observed "during and immediately after each injection," without a fixed number of minutes. [2]

Aveed vs Nebido: what is the difference?

The same drug in different amounts and on different rules:

[1], [2], [4]

How is it given, and can you inject it yourself?

No. Aveed is given only by a healthcare professional in a certified setting ("Your doctor will inject AVEED deep into the muscle of your buttock"), and UK and Australian guidelines say the 1000 mg products cannot be self-administered. [1], [16], [17], [18]

The labels describe a slow, careful injection:

• Site. Aveed goes into the gluteus medius, the muscle in the upper outer part of the buttock, avoiding the arteries and the sciatic nerve; the side alternates between injections. [1]
• Speed. Aveed over 60 to 90 seconds, after checking that no blood is drawn back; Nebido "very slowly (over two minutes)", warmed first according to the Society for Endocrinology. [1], [2], [17]
• Bleeding risk. The Nebido label reminds prescribers of the usual limits on muscle injections with bleeding disorders, and the Australian statement calls deep injection unsuitable with a clotting disorder or low platelets; one clinic saw no blood collections (hematomas) after 269 injections in men on blood thinners or antiplatelet drugs. [2], [18], [49]

This guide does not teach injection technique. How to inject testosterone covers sites and needles for the forms people inject themselves.

How should testosterone undecanoate injection be stored?

At room temperature, in the carton, and used as soon as it is opened. The leaflet in your box is the final word. [1], [2]

[1], [2]

Why it might look cloudy. Cold makes the oil thicker and cloudy for a while; the Nebido label says to bring it to room or body temperature and use only a clear solution. [2]

For carrying medicine on a trip, see traveling with testosterone; undecanoate's long interval often means an injection can be planned around travel instead.

What does testosterone undecanoate injection do to fertility, estrogen and red blood cells?

Each of these has its own hub guide; here is what is specific to undecanoate injections.

Fertility. The labels warn that testosterone suppresses sperm production and that the effect may be irreversible for some men. Undecanoate was even tested as a male contraceptive: in a Chinese trial of 1,045 healthy men, monthly 500 mg injections of a different undecanoate product (in tea seed oil) suppressed sperm to zero or near zero in 95% within 6 months, and sperm recovered in all but two after stopping. Because the depot lasts, recovery starts late. The AUA says testosterone should not be prescribed to men trying to conceive. See TRT and fertility and the hCG guide. [1], [50], [36], [14]

Estrogen. Some testosterone becomes estradiol, which rose in step with testosterone and stayed in the normal range in the German studies; Aveed's label lists "estradiol increased" in 2.6% of 153 men. No guideline sets a routine estradiol target. See estrogen on TRT. [31], [34], [1], [14]

Red blood cells. The evidence points both ways, from different kinds of studies:

• Across 29 randomized trials, a network meta-analysis found undecanoate injections raised hematocrit about 1.6 points more than placebo, vs about 4.0 for enanthate and cypionate injections and 3.0 for gel. [38]
• In one German registry of 802 men, not randomized, hematocrit went above 50% in 69 of 304 on undecanoate injections vs 25 of 498 on gel. [51]
• In T4DM, hematocrit went above 54% in 22% of men on testosterone (106 of 491) vs 1% on placebo (6 of 484). [27]
• In one clinic's routine practice, 25 of 347 men (7%) had hematocrit above 50% and 3 (1%) above 54%. [49]

The UK label adds that SGLT-2 inhibitor diabetes medicines can add to the rise. See hematocrit on TRT. [2]

What do we actually know about testosterone undecanoate injection in people?

That it restores testosterone is settled. Undecanoate injections also have one of the larger randomized trials of any testosterone form, T4DM, though it studied diabetes prevention rather than symptoms of low testosterone.

Which studies used undecanoate injections?

Heart safety rests mainly on TRAVERSE, a trial of gel (heart). [53] A 2014 meta-analysis of 33 undecanoate studies found better fat mass, blood sugar (HbA1c) and erectile function; changes in blood pressure, cholesterol and waist size appeared only in uncontrolled studies. [47]

What about the large registries?

Large observational studies of undecanoate are often quoted with dramatic results. Read them with care. Industry surveillance studies of 1,438 men in 23 countries (side effects in 6%) and 870 German men had no comparison group; the German one has a published correction we could not read. Long-running German registries reported large differences in weight, heart events and death between men who chose undecanoate and men who declined it, but men chose their own group and authors declared employment by the manufacturer, so the differences cannot be read as drug effects. [54], [55], [56], [57]

How does testosterone undecanoate injection work?

Once injected, the oil forms a depot in the muscle. The undecanoate ester slowly moves out of the oil into the blood, where enzymes called esterases cut off the undecanoic acid tail and free testosterone. That slow exit sets the 10 to 14 week interval. [1], [2]

Testosterone then acts like the body's own hormone; some is converted to dihydrotestosterone (DHT) and some to estradiol. [1]

Why it switches off your own production. The brain senses testosterone from any source. When levels are high, the pituitary lowers its LH and FSH signals to the testicles, so they make little testosterone and fewer sperm. [1]

Why it raises red blood cells. Androgens stimulate red blood cell production, so hematocrit rises on every form of testosterone. [1], [38]

What are the risks and unanswered questions?

Is testosterone undecanoate injection safe?

For men with a confirmed diagnosis, given in a clinic that follows the label, it is an established treatment with well-known risks. The risk specific to this form is a reaction during or just after the injection. The others are shared with all testosterone: more red blood cells, blood clots, higher blood pressure, prostate effects and loss of fertility. Long-term heart and prostate safety remain uncertain, since the largest safety trial used a gel: in TRAVERSE, heart attacks and strokes were no more common than on placebo, but atrial fibrillation, acute kidney injury and blood clots in the lung were, and it lasted under 2 years on average (see the heart section). [1], [2], [53]

Why does Aveed have a boxed warning? What is POME?

Aveed's boxed warning covers serious pulmonary oil microembolism (POME) and anaphylaxis, and it is the only US testosterone boxed warning about the injection itself. [1], [58], [59]

• What POME is. Tiny droplets of the injected oil reach the lungs. The label lists an urge to cough, shortness of breath, throat tightening, chest pain, dizziness and fainting, during or immediately after the injection. [1]
• Anaphylaxis is a severe allergic reaction, which can be life-threatening. [1]
• When it happens. After any injection, including the first, and not only early in treatment. [1], [20]
• Why the 30 minutes. FDA found that about 90% of severe reactions happened during the injection or within 30 minutes of it, so the label requires every patient to stay under observation in the clinic for 30 minutes. [20], [1]

How often do injection reactions happen?

Rarely, but the published numbers differ widely because they count differently:

• Aveed's own 84-week trial: 1 man had a mild coughing fit lasting 10 minutes after his third injection. [1]
• Across 18 clinical trials of 3,556 men, reviewers counted 9 POME events in 8 men and 2 episodes of anaphylaxis. [1], [20]
• The Nebido label: suspected POME after at least 1 in 10,000 and fewer than 1 in 1,000 injections in trials. [2]
• A clinic that watched every injection: Sydney nurses recorded POME after 56 of 3,022 injections (19 per 1,000) in 43 of 347 men; 66% were mild and 19% severe, 40% began before the injection was finished, and repeat reactions were more likely than chance. [49]
• Reports after Aveed's launch: 28 POME reports for 90,092 doses distributed over 4.3 years, under 0.1% per injection; 13 of 17 with a recorded end time resolved within 30 minutes. Voluntary reports miss many events, and two authors worked for the manufacturer. [60]

Doserly

Why oil-cough (POME) rates differ

Four ways of counting, four denominators. These rates cannot be pooled.

Watched every injection · per injectionSydney clinic, 1000 mg (Middleton 2015)

19 per 1,000 injections56 of 3,022 injections (95% CI 14–24). 43 of 347 men; 66% mild, 19% severe; 40% began before the injection finished.

Label trial data · per injectionNebido UK label (section 4.8)

RareAt least 1 in 10,000 and fewer than 1 in 1,000 injections. Suspected POME in clinical trials.

Adjudicated trials · per man18 clinical trials (Aveed label, FDA review)

8 of 3,556 men9 POME events; 2 anaphylaxis events. Counted per patient, not per injection.

Voluntary reports · per dose distributedAfter Aveed’s US launch, 2014–2018 (Pastuszak 2020)

28 reportsFor 90,092 doses: under 0.1% per injection. 13 of 17 with an end time resolved within 30 min; manufacturer-linked authors.

Watching every injection finds more mild events than waiting for reports. About 90% of severe reactions in FDA's review happened within 30 minutes.

How FDA decided. At an April 2013 advisory meeting, experts split 9 to 9 on whether the drug was safe for its use, and 17 of 18 voted that a slow injection plus 30 minutes in the office would not be enough on its own. FDA then approved Aveed in 2014 with the restricted REMS program. [20], [40]

What to do. Tell the nurse at once about any urge to cough, difficulty breathing, sweating, throat tightness, chest pain or dizziness, during or after the injection. Most episodes last a few minutes; some last hours and need emergency care, and the Aveed patient guide says to get emergency help if symptoms get worse over the 24 hours after an injection. In 3 of 4 postmarketing reports that needed an emergency visit, problems with injection technique or dosing were identified as a possible contributing factor. [1], [60]

POME can follow other oil injections too; in 2025 the European Union's safety committee recommended listing it as a rare effect for all oil-based testosterone injections. [61]

What side effects do the labels list?

In Aveed's 84-week study of 153 men, the most common side effects were:

[1]

Seven men (4.6%) stopped because of side effects. The Nebido label lists acne and injection-site pain as the most frequent, and names irritability, nervousness, weight gain and prolonged or frequent erections as signs of too much androgen. [1], [2]

Does testosterone undecanoate injection affect the heart?

No heart-outcome trial has tested undecanoate injections. The best evidence comes from TRAVERSE, a randomized trial of about 5,200 men aged 45 to 80 with heart disease or high heart risk, given daily testosterone gel or a placebo gel. Among the 2,596 men who used testosterone gel and the 2,602 who used placebo gel, it found:

• Heart attack, stroke or heart death (major adverse cardiovascular events, MACE): 182 men (7.0%) on testosterone vs 190 (7.3%) on placebo; hazard ratio 0.96, with a 95% confidence interval of 0.78 to 1.17. The top of that range stayed below the trial's safety margin of 1.5, so a large rise in risk was ruled out. [53], [1]
• Heart rhythm: atrial fibrillation 3.5% vs 2.4%; nonfatal rhythm problems needing treatment 5.2% vs 3.3%. [1]
• Kidneys: acute kidney injury 2.3% vs 1.5%. [1]
• Clots: venous clots 1.7% vs 1.2%, including pulmonary embolism 0.9% vs 0.5%. [1]
• Fractures: 91 of 2,601 men (3.50%) vs 64 of 2,603 (2.46%), counting every randomized man. [62]
• Blood pressure: systolic pressure rose 1.0 mm Hg on testosterone and fell 0.5 mm Hg on placebo by 36 months. [1]

Doserly

TRAVERSE: absolute results

Testosterone gel (2,596 men)Placebo gel (2,602 men)

Heart attack, stroke or heart death

Testosterone 7.0% vs placebo 7.3% (182 vs 190 men; hazard ratio 0.96, 95% CI 0.78–1.17; met the 1.5 safety margin)

Nonfatal rhythm problems needing treatment

Testosterone 5.2% vs placebo 3.3%

Atrial fibrillation

Testosterone 3.5% vs placebo 2.4%

Clinical fracture

Testosterone 3.5% vs placebo 2.5% (91 of 2,601 vs 64 of 2,603 in the full analysis set)

Acute kidney injury

Testosterone 2.3% vs placebo 1.5%

Venous clots (all)

Testosterone 1.7% vs placebo 1.2%

Pulmonary embolism

Testosterone 0.9% vs placebo 0.5%

About 5,200 men aged 45–80 at high heart risk; daily gel; mean treatment 21.7 months; about 61% stopped their study gel. Not a trial of injections.

Its limits matter for undecanoate. TRAVERSE tested only a gel, the average man used it for 21.7 months, about 61% stopped their study gel early, and it enrolled men at high heart risk. [53], [1]

Blood pressure on Aveed itself. In a 24-hour monitoring study, Aveed raised average blood pressure by 3.1/2.0 mm Hg after 16 weeks, and 8 of 222 men (3.6%) had high blood pressure reported as a side effect. The label advises against use with uncontrolled high blood pressure. [1], [63]

See TRT and heart health for the full picture.

What about blood clots, sleep apnea and fluid retention?

• Blood clots. The labels report clots in the legs (deep vein thrombosis) and lungs (pulmonary embolism); leg pain, swelling, warmth or redness, or sudden shortness of breath hours or days after an injection need urgent assessment. That is different from POME, which starts during or just after the injection. [1], [2]
• Sleep apnea. In obese men with severe sleep apnea, undecanoate injections worsened night-time drops in oxygen at 7 weeks, though not at 18. In a T4DM follow-up survey, a new sleep apnea diagnosis during the trial was more common on testosterone (3.0% vs 0.4%). [64], [37]
• Fluid retention. Swelling, with or without heart failure, can be serious in people with heart, kidney or liver disease. [1]

Could testosterone undecanoate injection affect the prostate?

Testosterone can enlarge the prostate and raise PSA. In Aveed's 84-week study, average PSA rose from 1.0 to 1.5 ng/mL, 14 men (10.9%) went from below 4 to above 4 ng/mL, and prostate cancer was found in 2 men (1.3%); there was no comparison group. In TRAVERSE, which excluded men with PSA above 3.0 ng/mL, high-grade prostate cancer occurred in 5 of 2,596 men on testosterone (0.19%) vs 3 of 2,602 on placebo (0.12%), a difference that was not significant. [1], [65]

US labels rule out testosterone in known or suspected prostate cancer; the UK label words it as "androgen-dependent carcinoma of the prostate". See TRT and the prostate. [1], [2]

Is testosterone undecanoate injection legal? Is it FDA approved?

Checked September 2026. Rules differ by country and change often.

United States. Aveed is FDA-approved and testosterone is a Schedule III controlled substance. The key steps:

• 2014. Aveed approved on March 5 with its REMS, last modified October 8, 2024. [40], [43], [66]
• February 28, 2025. FDA added TRAVERSE results and blood-pressure warnings to testosterone labels; Aveed's label took them in July 2025. [63], [44]
• June 18, 2026. The Department of Health and Human Services (HHS) announced that FDA is requesting label changes: removing the age-related limitation, contraindicating testosterone only in metastatic prostate cancer, and revising the prostate-enlargement warning. These are requests; the current Aveed label still carries the old wording. [67], [1]
• Telehealth. Temporary rules let clinicians prescribe controlled medicines without an in-person visit through December 31, 2026, but Aveed itself must still be injected in a certified healthcare setting. [68], [42]

Canada. Testosterone is a Schedule IV controlled substance. No injectable testosterone undecanoate is marketed; the undecanoate sold there is oral capsules. [69], [9]

United Kingdom. Testosterone is a Class C controlled drug (Schedule 4 Part II), prescription-only. Nebido and Roxadin have current UK product information. [70], [2], [3]

Australia. Testosterone is a Schedule 4 (prescription-only) medicine with extra controls on possession. Reandron 1000, Rejunon 1000 and Gonadron have current product information, and the injection is PBS-listed with authority (cost). [71], [4], [48]

European Union. Rules are national. France reimburses a generic but not Nebido, Spain funds a generic, the Netherlands has reimbursed Nebido since October 1, 2022, and Ireland needs a new prescription for each supply. See TRT in Europe. [7], [8], [72], [73]

A "research use only" label on a vial does not make it legal, tested or the same as a licensed product.

Is testosterone undecanoate banned in sport?

Yes. Testosterone and its esters are on the World Anti-Doping Agency (WADA) Prohibited List in class S1, banned in and out of competition, and the 2027 list keeps that from January 1, 2027. The Nebido label warns athletes that it can cause a positive doping test. A therapeutic use exemption is granted only when low testosterone has an organic cause (such as a testicular or pituitary disorder), not for age, obesity or earlier steroid use. [74], [75], [2], [76]

Who should be especially cautious?

• Men who want children now or soon. Testosterone suppresses sperm production, and after undecanoate the suppression outlasts the last injection by months. [14], [36]
• Men who want to be able to stop quickly. A depot cannot be removed. [17]
• Allergy to castor oil or benzyl benzoate, or earlier reactions to injections. Known allergy to the ingredients rules it out. [1]
• Bleeding disorders or low platelets. Deep muscle injections need care; see how it is given. [2], [18]
• Prostate or breast cancer, or liver tumors. Contraindicated on current labels (liver tumors on the UK label). [1], [2]
• Heart, kidney or liver disease, or high blood pressure. These can worsen. [1]
• High hematocrit, sleep apnea or obesity. A BMI of 30 or more was linked to less favorable safety values in one long-term German study. [77]
• Epilepsy or migraine. The UK label says these can be aggravated. [2]
• Women and children. Contraindicated in pregnancy; these guides are for men. Safety and benefit under 18 have not been established; any use in older teenagers, such as inducing puberty, is for a specialist, and the Society for Endocrinology says the early loading injection is left out then. [1], [17]
• Drug-tested athletes. Banned at all times. [74]

Can testosterone undecanoate be taken with other medicines?

The labels list these interactions:

• Blood thinners (warfarin and other oral anticoagulants). Testosterone can change their effect; the Aveed label advises more frequent clotting tests (INR and prothrombin time), especially when starting and stopping. [1], [2]
• Insulin and diabetes medicines. Testosterone can lower blood sugar and insulin needs. [1]
• SGLT-2 inhibitors (a type of diabetes medicine). The UK label warns the combination has been linked to more erythrocytosis and advises monitoring hematocrit. [2]
• Corticosteroids. Together they can increase fluid retention. [1]

Testosterone can also lower thyroxine-binding globulin, which changes total thyroid hormone results without changing thyroid function. Bring a full list of everything you take, including supplements, to a pharmacist or doctor. [1]

Is it available, and what does it cost?

Checked September 2026. Official figures only; what you pay depends on your country, insurance and clinic fees.

• United States. Medicare's Part B payment limit for Aveed is $2.149 per mg for July to September 2026, about $1,612 for a 750 mg injection, and $2.203 per mg (about $1,652) from October 1, 2026, before the clinic's fee; the same July list prices cypionate at 2.5 cents per mg. Medicare Part B spent about $1,361 per Aveed claim in 2024. FDA lists no testosterone shortage. [78], [79], [80]
• Australia. PBS item 10205D needs an authority: men without a known pituitary or testicular disorder must be 40 or older, with testosterone below 6 nmol/L on two morning tests (or 6 to 15 nmol/L with a high LH), and a named specialist. The government price is A$92.91; a general patient pays up to A$25.00. Short shortages of Gonadron and Rejunon 1000 in mid-2026 are resolved. [48], [81], [82]
• United Kingdom. NHS prescriptions in England cost £9.90 per item. [83]
• France. The generic 1000 mg injection costs €21.88 before the dispensing fee and is reimbursed at 65%; Nebido is not reimbursed. [7]
• Canada. Not available as an injection. [9]

What should be monitored while using testosterone undecanoate injection?

Labels ask for blood tests before and during treatment; guidelines supply the numbers. Use this to prepare questions for your prescriber; it is not a personal testing plan. [1], [2]

[1], [2], [13], [15], [18]

The Society for Endocrinology repeats testosterone and a full blood count every 3 to 5 injections or yearly after the first check, and the EAU monitors testosterone and hematocrit at 3, 6 and 12 months, then yearly. [17], [15] See TRT blood work and hematocrit on TRT.

What do people in public communities report?

Public forums hold every kind of undecanoate story: men who feel steady for the first time on treatment, men who feel it fading weeks before the next injection, and men who switched away. The accounts below come from public Reddit threads from the past year, mostly about Nebido and Reandron, and are described without identifying anyone.

What do the positive reports look like?

Steady energy and sex drive with few injections. A man with Kallmann syndrome (a condition present from birth in which the brain does not trigger puberty) returned to Nebido after using gel; on 8-week intervals, his trough before the fourth injection was 19.2 nmol/L, with better energy, libido and sexual function. Another described two years of clear benefit after gel and pellets, though weight loss, new exercise and stopping antidepressants happened over the same period. [84], [85]

Early reports are mixed. One man starting Nebido for low testosterone and low mood noticed better mood and motivation but still had some low days after his second injection. [86]

Does it wear off before the next injection?

This is the most common theme, and the experiences vary:

• Fading by weeks 4 to 6. One man on 1000 mg every 3 months, then every 2, felt good for about a month after each injection and tired by week 6. Another's total testosterone was 6 nmol/L just before his 6-week second injection. [87], [88]
• The last two weeks. One man on 10-week intervals described depressed mood, anxiety and afternoon sleepiness in the final two weeks; 8-week intervals had raised his blood count. [85]
• Low results before the next dose. On Aveed, one man's level 10 weeks after his second injection was 225 ng/dL. Another on Nebido reported about 1,000 ng/dL after an injection and about 300 ng/dL before the next; his doctor would not change the schedule. [89], [90]

Replies in several threads suggest shorter intervals, and some men describe 8-week gaps. [91], [84], [85] The threads rarely include a trough drawn at the right time with a unit, which is what prescribers use to decide (timing).

What happens when people split the vial?

Some prescribers have agreed to smaller doses outside the labels, and the results are mixed:

• One man who felt poorly by week 8 moved to 250 mg every 14 days from prescribed Nebido; a later test showed 26.4 nmol/L, and he continued. [92]
• A man treated after testicular cancer started 500 mg every 5 to 6 weeks with his endocrinologist; he described 1 to 2 days of muscle soreness after injections, much less after changing position. [93]
• One doctor worried about dividing a 4 mL container accurately. [94]

No study has tested these schedules (splitting the vial), and some add up to more testosterone a week than any label: 250 mg every 14 days averages 125 mg a week, while Aveed averages 75 mg and the 1000 mg products 71 to 100 mg.

What unwanted effects come up?

• After the first injection. One man reported headaches, much more anxiety and higher blood pressure two weeks after his first injection; another had a hangover-like feeling, water retention and insomnia by day 4, alongside better mood. [95], [96]
• Acne. One man with a pituitary condition developed marked facial and back acne on 3-monthly Nebido, with fatigue and low libido returning near each injection; he later stopped and tried a gel. [97]
• Headaches and blood counts. One man had headaches and a rising hematocrit on Nebido, then felt better on another ester until his hematocrit reached 52.1%. [98]

None of the threads in this set described an oil cough (POME) during an injection, so the figures in the risks section rest on labels and studies.

What do people report about switching, supply and access?

Undecanoate is often the only injection offered locally, and switching is common. One man who moved from the United States to Europe had to change from cypionate to Nebido; another in France considered returning to enanthate during a Nebido shortage. One wife asked about an instruction for her husband to inject 3 mL of Aveed at home monthly, which differs from the label (given in a certified clinic, every 10 weeks after the 4-week dose). [99], [100], [101]

One man whose specialists stopped Nebido after 18 months to reassess his own production described severe symptoms and low levels 18 months later. [102] Threads about non-prescribed doses above replacement are outside this guide (TRT vs steroids).

How can you judge an undecanoate story?

Ask: Aveed or a 1000 mg product, and the whole container? How many weeks after the injection was blood drawn, and in which unit (ng/dL, nmol/L or ng/mL)? Is the schedule still in its first months, before levels settle? What else changed, such as weight, sleep or other medicines? What happened months later?

These selected discussions show what people experience and the questions research should answer. They are not a survey of all users, a success rate or a substitute for the studies.

How does testosterone undecanoate injection compare with other testosterone forms?

These are the forms most often weighed against undecanoate injections. Status was checked in September 2026.

No trial ranks these forms on long-term outcomes; in the one randomized comparison, sexual function improved as much on undecanoate as on enanthate. [24] The practical differences are how often you dose, who gives it, how much levels swing, how easily treatment stops and how much hematocrit rises. See Sustanon 250 for the mixed-ester injection.

Common questions about testosterone undecanoate injection

How long does one testosterone undecanoate injection last?

About 10 to 14 weeks. Aveed is given every 10 weeks after the 4-week second dose, and the 1000 mg products every 10 to 14 weeks, most often about 12. Levels peak about a week after the injection and fall slowly, and the depot keeps releasing some testosterone for months. [1], [2], [19] See typical protocols.

What is the difference between Aveed and Nebido?

The same drug in different amounts and under different rules. Aveed (US) is 750 mg in 3 mL on a fixed schedule, given only in certified clinics with 30 minutes' observation. Nebido and other 1000 mg brands (UK, Europe, Australia) are 1000 mg in 4 mL every 10 to 14 weeks, adjusted by the trough level. [1], [2], [42] See Aveed vs Nebido.

Can I inject Aveed or Nebido myself?

No. Aveed is given only by a healthcare professional in a certified setting, and UK and Australian guidelines say the 1000 mg products cannot be self-administered, because of the slow, deep injection and the need to watch for an oil cough or allergic reaction afterwards. [1], [42], [16], [17], [18] See how it is given.

What does POME feel like, and why do I have to wait 30 minutes?

POME usually feels like a sudden urge to cough or a coughing fit, sometimes with difficulty breathing, throat tightness, chest pain, sweating or dizziness, during or just after the injection. Most episodes last a few minutes. About 90% of severe reactions in FDA's review happened within 30 minutes, which is why Aveed requires a 30-minute wait. Tell the nurse at once if anything feels wrong. [1], [20], [49] See the oil cough.

Why do I feel worse in the last weeks before my injection?

Some men feel symptoms return before the next injection; no study has measured how often. The level is lowest then, varies between men and is lower on average in heavier men. Prescribers check a trough drawn just before the injection and, outside the US, can shorten the interval if it is low; other causes of fatigue are worth ruling out too. [1], [2], [19] See wearing off.

Can Nebido be split into smaller, more frequent doses?

No label or guideline describes it. Each ampoule or vial is single use, to be injected immediately after opening; the Australian labels allow a smaller volume when levels are high, but not dividing a vial into weekly doses; and no published study has tested divided doses. For weekly dosing, cypionate and enanthate come in multi-dose vials. [2], [1], [4] See splitting the vial.

Is injectable testosterone undecanoate the same as Jatenzo or Kyzatrex?

No. The capsules contain the same ester, but they are swallowed twice a day with food and absorbed through the gut's lymph vessels, at completely different doses. The injection is a castor-oil depot given every 10 to 14 weeks. They are not interchangeable. [11], [104], [1] See oral testosterone.

What if an injection is late?

US labels give no missed-dose instruction, and the Nebido leaflet says not to miss injection appointments. Levels are already at their lowest near the end of an interval, so a late injection means more time at a low level; if a blood test is due, tell the prescriber when your last injection actually was. [106], [1]

Glossary

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

Acne

Spots and blocked pores caused partly by androgens, which increase oil production in the skin. It was the most common side effect in Aveed's long-term study.

Anaphylaxis

A severe, whole-body allergic reaction that can affect breathing and blood pressure and can be life-threatening. It is one of the two reactions in Aveed's boxed warning.

Boxed warning

The strongest warning on a US drug label, printed in a box at the top. Aveed's covers oil reaching the lungs and severe allergic reactions.

Controlled substance

A medicine whose prescribing and possession are restricted by law because it can be misused. Testosterone is Schedule III in the US, Schedule IV in Canada and Class C in the UK.

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.

Depot

A pool of medicine left in the body, such as oil in a muscle, that releases the drug slowly over days, weeks or months.

Dose (amount each time)

The amount given on one occasion. On the US and UK labels for testosterone undecanoate injection it is one whole vial or ampoule; the Australian labels also allow a smaller volume when levels are high.

Ester

A chemical tail joined to testosterone that makes it dissolve in oil and release slowly after injection. The body removes the tail to free testosterone. Undecanoate is the longest ester used in testosterone injections.

Estradiol

The main form of estrogen. In men it is made mostly from testosterone, so it rises when testosterone rises.

FSH (follicle-stimulating hormone)

A pituitary hormone that acts on the cells supporting sperm production. Testosterone therapy lowers it.

Half-life

The time it takes for the level of a substance to fall by half. For undecanoate injections, published figures range from about 34 to 90 days depending on what was measured; they describe the depot, not testosterone itself.

Hematocrit

The share of the blood made up of red blood cells. Testosterone raises it, and most guidelines act when it reaches about 54%.

Hypogonadotropic hypogonadism

Low testosterone because the brain and pituitary send too little LH and FSH to the testicles. It can be present from birth or start later. Also called secondary hypogonadism.

Hypogonadism

Low testosterone caused by a problem in the testicles or in the brain and pituitary signals that control them, confirmed with symptoms and repeated morning blood tests.

Intramuscular (IM)

Injected into a muscle. Testosterone undecanoate is injected deep into the buttock muscle.

LH (luteinizing hormone)

A pituitary hormone that tells the testicles to make testosterone. Testosterone therapy switches it off.

Loading dose

An early extra injection that brings levels up to a steady pattern sooner, such as Aveed's second injection at 4 weeks or an optional second Nebido injection at 6 weeks.

MACE (major adverse cardiovascular events)

A combined measure used in heart-safety trials. In TRAVERSE it meant heart attack, stroke or death from heart disease.

Placebo

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

Pulmonary oil microembolism (POME)

Tiny droplets of injected oil reaching the lungs, causing a sudden urge to cough, breathlessness or dizziness during or soon after the injection. It is the main reason for Aveed's boxed warning.

Primary hypogonadism

Low testosterone because the testicles themselves do not work well, even though the pituitary sends plenty of LH and FSH.

PSA (prostate-specific antigen)

A blood test for a protein made by the prostate. It rises slightly on testosterone and is used to decide whether prostate checks are needed.

REMS (Risk Evaluation and Mitigation Strategy)

A US safety program FDA can require for a medicine with serious risks. Aveed's requires trained prescribers, certified clinics and 30 minutes' observation after every injection.

Steady state

The point when levels follow the same pattern from one interval to the next. On Aveed it is reached with the third injection at week 14.

Subcutaneous (SC)

Injected into the fatty layer just under the skin. It is not a labeled route for testosterone undecanoate injection.

Tentative approval

An FDA decision that a generic meets the scientific standards but cannot yet be sold, often because of patents or exclusivity. A generic undecanoate injection has held one since 2016.

Titration

Adjusting a dose or schedule in steps, usually based on blood tests and symptoms. For undecanoate, the interval usually changes rather than the dose.

Trough level

The lowest level of a drug in the blood, measured just before the next dose. Labels and most guidelines judge undecanoate injections by it.

TRT (testosterone replacement therapy)

Prescribed testosterone, by injection, gel or other forms, for men with low testosterone. It switches off the brain's LH and FSH signals.

WADA

The World Anti-Doping Agency, which publishes the list of substances banned in sport. Testosterone is banned at all times.

Weekly total

All the amounts given in one week, added together. For long-acting injections it is an average for comparison: 750 mg every 10 weeks averages 75 mg a week.

How this guide was researched

This guide is built from a thorough review of the sources cited throughout it: product labels from the United States, the United Kingdom, Australia, France and Spain, FDA approval and safety-program documents, clinical guidelines from the United States, the United Kingdom, Europe and Australia, published clinical trials and studies, and government price and reimbursement records. We also reviewed public online forums where people describe their own experiences with testosterone undecanoate injections.

The guide cites 106 sources, including 13 product labels and leaflets, 7 guidelines and position statements, and 34 original studies in people, plus 19 public community threads. Each type of source answers a different question. Labels, guidelines and trials show what was approved and measured. Practice papers show how prescribers typically use it. 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