Low Testosterone: The Definitive Guide

What is low testosterone?

Low testosterone, called male hypogonadism by doctors, is when the testes make too little testosterone and it causes symptoms. It is diagnosed only when symptoms or signs come together with blood levels that are clearly low on at least two separate early-morning tests. The cause lies either in the testes or in the brain's signal to them. [1], [2], [5]

Testosterone is the main male sex hormone. It drives sex drive and erections, supports sperm production, and helps maintain muscle, bone, body hair and red blood cells, which is why a shortage can show up in so many different ways. [1]

How does the body make testosterone?

It works like a relay. The hypothalamus, at the base of the brain, sends a signal called GnRH to the pituitary gland just below it. The pituitary answers with two hormones: LH, which tells the Leydig cells in the testes to make testosterone, and FSH, which, together with the high testosterone level inside the testes, drives sperm production. When testosterone in the blood rises, the brain turns its signals down, like a thermostat. [13], [1]

That chain explains the two main types:

• Primary hypogonadism. The testes themselves are damaged, so testosterone is low even though the pituitary is sending plenty of LH and FSH. Blood tests show low testosterone with high LH and FSH. [1], [5]
• Secondary hypogonadism. The testes are fine, but the hypothalamus or pituitary sends too little signal. Testosterone is low and LH and FSH are low or "inappropriately normal", meaning not raised the way they should be when testosterone is low. [1], [5]

Doctors also sort causes into organic (disease or damage, usually permanent) and functional (something that suppresses the system and may reverse, such as obesity, opioid painkillers or serious illness). A functional cause can sometimes be fixed without testosterone. [1], [14]

In the European Male Ageing Study (EMAS) of 3,369 men aged 40–79, 11.8% had the secondary kind and 2.0% the primary kind; another 9.5% had normal testosterone with a high LH (compensated hypogonadism), a pattern whose meaning is still unclear. [8], [15]

Where is testosterone in the blood?

Most testosterone in the blood is attached to proteins. In classic measurements, 43–45% was bound tightly to SHBG (sex hormone-binding globulin), 53–55% loosely to albumin, and about 2% floated free (free testosterone); the Endocrine Society puts the free share at 2–4%. Free and albumin-bound testosterone together are called bioavailable testosterone, the part tissues can use easily. A standard blood test measures total testosterone, all of it together. [16], [1]

How is low testosterone diagnosed?

With three things together: symptoms or signs of testosterone deficiency, a total testosterone level below the guideline cut-off on at least two separate early-morning tests (most guidelines also ask for fasting), and further tests to find the type and the cause. US product labels ask for the same two-morning confirmation before treatment starts. [1], [2], [5], [3]

What are the symptoms of low testosterone?

The Endocrine Society sorts symptoms and signs by how strongly they point to low testosterone:

[1]

Sexual symptoms are the most telling. In EMAS, only low sexual desire, fewer morning erections and erectile dysfunction were linked with low testosterone as a group, and the European Association of Urology (EAU) calls sexual symptoms the most specific. Tiredness, poor sleep, low mood and weight gain have many causes, which is why symptoms alone are not diagnostic. [7], [5], [4]

Erectile dysfunction and low testosterone overlap, but not always. The EAU puts coexisting low testosterone at about 30% of men with erectile dysfunction, and the answer depends on the line drawn: among 2,794 such men at one center, 23% were under 300 ng/dL and 47% under 400. [5], [17]

Who should get their testosterone checked?

Men with symptoms, and some groups at higher risk. Guidelines disagree on whether men at risk but without symptoms should be tested.

• No routine screening. The Endocrine Society (2018 and its 2026 statement) advises against screening men in the general population, and the EAU tests only men with symptoms. [1], [4], [5]
• High-risk groups. The Endocrine Society suggests testing men with pituitary disease, men taking opioids or steroid (glucocorticoid) medicines, men coming off anabolic steroids, and men with HIV-related weight loss, infertility, osteoporosis, low sex drive or erectile dysfunction. [1]
• The American Urological Association (AUA) goes further. It suggests testing even without symptoms in men with unexplained anemia, bone loss, diabetes, past chemotherapy or testicular radiation, HIV/AIDS, long-term opioid or corticosteroid use, infertility or pituitary disease. So a man with diabetes may be tested at a routine visit under the AUA approach, but only once symptoms appear under the others. [2]

Symptom questionnaires do not diagnose it. The ADAM questionnaire caught 88% of men with low testosterone but also flagged 4 in 10 men with normal levels, and the AUA, the Endocrine Society and the EAU advise against using questionnaires for diagnosis. [18], [2], [1], [5]

What testosterone level counts as low?

This table shows the line in every major clinical guideline, plus the Australian subsidy rule and the US labels, checked September 2026. Every body also requires symptoms or signs.

[2], [1], [4], [19], [5], [20], [6], [21], [22], [14], [23], [24], [3]

Nearly every body wants symptoms plus at least two low morning tests (the Australian position statement accepts one clearly diagnostic result). North American bodies land at about 264–300 ng/dL, most European bodies at 12 nmol/L (about 350 ng/dL), the Canadian Urological Association at 10 nmol/L, and the UK Society for Endocrinology uses bands rather than one line. [2], [1], [5], [22], [21]

Doserly

Where guidelines draw the line for low testosterone

Total testosterone below which each body supports a diagnosis, with symptoms.

Each line runs from 200 ng/dL (7 nmol/L, left) to 400 ng/dL (14 nmol/L, right); the shaded part is 264–350 ng/dL, where the guidelines' lines fall. A dashed circle means an approximate line.

Endocrine Society (2018)

Below 264 ng/dL (9.2 nmol/L), standardized assays

CUA (Canada, 2021)

Below 10 nmol/L (about 290 ng/dL)

AUA (US, 2018, reconfirmed 2024)

Below 300 ng/dL (10.4 nmol/L)

Endocrine Society statement (July 2026)

“Near 300 ng/dL”

EAU · ICSM · BSSM (Europe 2026 · international 2024 · UK 2023)

Below 12 nmol/L (about 350 ng/dL)

Every guideline also requires symptoms, and all but the CUA call for at least two morning tests; none diagnoses from a number alone.

Why do guidelines disagree on the number?

Because labs used to measure testosterone very differently, and because the bodies chose their lines by different methods.

• Lab differences. When 1,133 laboratories measured the same sample from one man, results ranged from 45 to 365 ng/dL. That is why the Endocrine Society ties its line to assays certified by the US Centers for Disease Control and Prevention (CDC). [1]
• Healthy ranges. The 264 ng/dL line is the bottom 2.5% of healthy, non-obese men aged 19–39, measured on one calibrated scale. [25], [1]
• Treatment benefit. European bodies put the line where trials found benefit: the EAU says testosterone therapy is ineffective above 12 nmol/L and helps most below 8 nmol/L. [5], [21]

Between about 8 and 12 nmol/L (230–350 ng/dL) is a grey zone, where the BSSM accepts a trial of treatment and the European Academy of Andrology (EAA) asks for a free testosterone test. [6], [14]

Units. US labs report ng/dL and most other countries nmol/L; 1 nmol/L equals 28.84 ng/dL, so 12 nmol/L is about 346 ng/dL. The testosterone unit converter does the arithmetic.

What is a normal testosterone level for your age?

In men without obesity, the median total testosterone is about 530 ng/dL at 19–39 and about 480 ng/dL from 40 on. The bottom of the range falls with age; the top stays about the same. These figures come from four US and European studies (9,054 men in all, 6,933 of them without obesity) measured on one calibrated scale. [25]

[25]

Including men with obesity, the medians are lower at every age (507 ng/dL at 19–39, 446 ng/dL from 50). For healthy young men aged 19–39, the range covering the middle 95% was 264–916 ng/dL, the range the Endocrine Society adopted. [25], [1]

Doserly

Normal testosterone by age

Total testosterone in men without obesity: low end (2.5th percentile), median and high end (97.5th percentile).

Each bar runs from 100 ng/dL (left) to 1,000 ng/dL (right); the band is the low end to the high end, and the dark tick is the median.

19–39 years

267 (9.3 nmol/L) to 929 ng/dL; median 531 ng/dL (18.4 nmol/L)

40–49 years

235 (8.1 nmol/L) to 929 ng/dL; median 481 ng/dL (16.7 nmol/L)

50–59 years

219 (7.6 nmol/L) to 929 ng/dL; median 477 ng/dL (16.5 nmol/L)

60–69 years

218 (7.6 nmol/L) to 929 ng/dL; median 477 ng/dL (16.5 nmol/L)

70–79 years

218 (7.6 nmol/L) to 926 ng/dL; median 477 ng/dL (16.5 nmol/L)

80–99 years

157 (5.4 nmol/L) to 913 ng/dL; median 476 ng/dL (16.5 nmol/L)

Population ranges, not diagnostic cut-offs: guidelines use one line for all adult ages.

Age ranges are not cut-offs. Guidelines use one line for all adult ages. The Massachusetts Male Aging Study proposed age-specific lower limits (251 ng/dL in the 40s down to 156 ng/dL in the 70s), but no major guideline has adopted them, and the Endocrine Society's 2026 statement says the diagnosis is made the same way at any age. [26], [4]

How should the testosterone blood test be done?

Early in the morning, fasting, when you are well, and repeated on a different day. Each rule has a reason:

• Morning. Testosterone is highest in the morning. In men aged 30–40 it was 20–25% lower at 4 pm than at 8 am, a gap that shrank to about 10% by age 70, and 17 men with an afternoon result under 300 ng/dL were normal on all three morning tests. Guideline windows run from 6–10 am (VA) to before 11 am (EAA); night-shift workers are tested after a normal sleep period. [27], [19], [14], [5]
• Fasting. In one study, a sugary glucose drink lowered average testosterone by 25%, and it was still lower 2 hours later; 10 of 66 men (15%) with normal levels dropped into the low range. The EAU says a non-fasting test can underestimate total testosterone by more than 30%. [28], [5]
• Repeated. In the Endocrine Society's review, 30% of men with a first low result were normal on a repeat test, and two tests in the same man often differ by more than 18–28%. In 96 healthy men aged 55 and older tested four times in a year, only 1 of 25 with a first result under 10 nmol/L stayed under 10 at every later test. [1], [29], [30]
• When you are well. Testosterone fell below normal for a sustained period in 62% of acutely ill men in hospital, so the Endocrine Society advises against testing during or soon after an acute illness or short-term opioid use. [31], [1]
• With a reliable lab. The Endocrine Society's 2026 statement asks for a CDC-certified assay; LC-MS/MS (mass spectrometry) is the most accurate method. [4], [5]
• Without biotin. High-dose biotin supplements can disturb some hormone tests; the Endocrine Society advises stopping them at least 72 hours before LH and FSH tests. [1]

What do free testosterone and SHBG add?

They show how much testosterone is actually available when total testosterone is misleading, which happens when SHBG, the protein that carries most testosterone, is unusually high or low. [1], [5]

• Low SHBG (total testosterone reads low while free may be normal): obesity, type 2 diabetes, glucocorticoid and androgen medicines, an underactive thyroid and some rarer conditions. [1], [5]
• High SHBG (total can look normal while free is low): ageing, HIV, liver disease, an overactive thyroid, some anti-seizure medicines and estrogens. [1], [5]

Obesity is the everyday example: in one study, men with obesity had lower total testosterone than men without (10.5 vs 14.1 nmol/L) but the same calculated free testosterone. In EMAS, men whose total testosterone fell but free stayed normal did not develop new sexual symptoms; only men whose free testosterone also fell did. [32], [33]

When and how. Guidelines measure free testosterone when SHBG is likely to be altered or total testosterone is borderline (roughly 200–400 ng/dL, or 8–12 nmol/L). It should come from equilibrium dialysis, a reference lab method, or be calculated from total testosterone, SHBG and albumin; the two agree closely. "Direct" free testosterone kits are inaccurate, and the free androgen index is not a reliable measure in men. [1], [14], [34]

Free testosterone lines. The EAU uses 220 pmol/L (about 64 pg/mL) with limited evidence behind it, the BSSM 225 pmol/L, and the EAA calls 220 pmol/L not validated. [5], [7], [6], [14]

Are home finger-prick and saliva tests accurate?

Not for a diagnosis. Every guideline in this guide diagnoses low testosterone with a blood sample from a vein, and none uses finger-prick or saliva results. [1], [5], [2]

The one recent validation of a dried-blood-spot method matched venous serum closely in 20 people, but the blood was drawn from a vein and spotted onto cards in the lab, so it did not test real finger-pricks at home. Saliva testosterone has its own reference ranges, and we found no study comparing it with serum at the cut-offs guidelines use. A home test can prompt a proper test; it cannot replace one. [35], [36]

How do doctors find the type and the cause?

The next step after two low morning results is working out where the chain is broken:

1. LH and FSH, for everyone. High LH and FSH point to the testes (primary); low or normal LH and FSH point to the brain and pituitary (secondary). [1], [2], [5]
2. If secondary: prolactin and iron. A high prolactin can mean a prolactin-making pituitary tumor; the AUA measures prolactin when LH is low or low-normal and refers men with a persistently high result to an endocrinologist. The Endocrine Society adds iron tests to look for iron overload, and other pituitary hormones if needed. [2], [1]
3. If primary with very small testes: a chromosome test (karyotype) for Klinefelter syndrome. [1]
4. A pituitary MRI in selected men: when total testosterone is under 150 ng/dL with low or low-normal LH, when prolactin stays high, when other pituitary hormones are affected, or with headaches or vision loss (AUA, Endocrine Society). The EAU suggests one in severe secondary cases under 6 nmol/L. [2], [1], [5]

When is a brain scan likely to find something? Mostly when testosterone is very low or prolactin is high. Among 164 men with erectile dysfunction and repeatedly low testosterone, scans found a potentially serious lesion in 11 (6.7%), and the larger tumors were all in men at 104 ng/dL or less. In another 51 men, 3 of the 4 with a small tumor had prolactin more than twice the upper limit of normal. [37], [38]

What causes low testosterone?

Anything that damages the testes (primary) or quiets the brain's signal to them (secondary). In middle-aged and older men, the secondary kind is far more common, and it is usually linked to obesity, other illness or medicines rather than a disease of the pituitary. In EMAS, a BMI of 30 or more was strongly linked with secondary low testosterone (relative risk ratio 8.74). [8], [1]

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Where low testosterone starts

The chain: hypothalamus (GnRH) → pituitary (LH, FSH) → testes (testosterone, sperm), with testosterone feeding back to turn the signal down.

Secondary: brain and pituitary

Testosterone low · LH and FSH low or normal

Organic (disease or damage, usually lasting)

• Pituitary or hypothalamus tumor
• High prolactin (prolactinoma)
• Present from birth, including Kallmann syndrome
• Iron overload (hemochromatosis)

Functional (may reverse)

• Obesity and type 2 diabetes
• Opioids and steroid tablets
• Serious illness
• Poor nutrition or excessive exercise
• After stopping anabolic steroids

Primary: the testes

Testosterone low · LH and FSH high

Examples

• Klinefelter syndrome (47,XXY)
• Undescended testes
• Orchitis, injury or torsion
• Chemotherapy or radiotherapy
• Removal of the testes

Functional causes can reverse when the cause is treated.

What damages the testes themselves?

• Klinefelter syndrome (an extra X chromosome, 47,XXY). The most common genetic cause. In a Danish national registry it affected about 153 in 100,000 males (about 1 in 650), but only about 1 in 4 adult men with it had been diagnosed, and fewer than 10% before puberty. [39], [5]
• Other testicular causes: undescended testes, inflammation (orchitis, for example after mumps), injury or twisting (torsion), removal of the testes, myotonic dystrophy (an inherited muscle disease) and ageing. [1]
• Cancer treatment. After testicular cancer, 11% of men treated with surgery alone had low testosterone, against 37% of those who also had chemotherapy and radiotherapy; in survivors followed for decades, it rose from 12% to 41%, against 5% to 11% in similar men without cancer. [40], [41]
• Varicocele (enlarged veins around a testicle). The evidence conflicts: linked with low testosterone in one clinic study, but not in 7,035 young men from the general population. [42], [43]

What switches off the brain's signal?

• Pituitary and hypothalamus disease. Tumors, diseases that infiltrate or damage the area, and pituitary surgery or radiation. [1]
• High prolactin. A prolactin-making pituitary tumor (prolactinoma) switches off the signal to the testes. [1], [38]
• Present from birth. Congenital hypogonadotropic hypogonadism, sometimes with a poor or missing sense of smell (Kallmann syndrome). [1], [2]
• Iron overload (hemochromatosis), mainly when advanced: in 141 men with the inherited form, 9 had low testosterone, 8 of them with cirrhosis. [44], [1]
• Functional causes, which may reverse: obesity, some sleep disorders, serious illness and organ failure, heavy alcohol or marijuana use, poor nutrition or excessive exercise, and some medicines (next section). [1]

Which medicines can lower testosterone?

• Opioid painkillers. In a review of 15 studies (3,250 patients), 63% of men using opioids had low testosterone. The Endocrine Society says nearly all opioids suppress it at doses equal to 30 mg of methadone a day, buprenorphine less so, and since 2016 US opioid labels warn about it. [9], [1], [45], [46]
• Steroid (glucocorticoid) tablets. Testosterone was 33% lower in men on long-term prednisolone tablets (14.5 vs 21.7 nmol/L), but not significantly lower with inhaled steroids. [47]
• Anabolic steroids, after stopping. About 2.5 years after stopping, 27% of former users still had testosterone below 12.1 nmol/L. See TRT vs steroids. [48]

Do not stop a prescribed medicine on your own: opioids and steroid tablets need a supervised plan.

How do weight, diabetes and sleep apnea affect testosterone?

They are the most common everyday drivers, and they often travel together.

• Obesity. In a US primary care study of men aged 45 and older, men with obesity had 2.38 times the odds of a result under 300 ng/dL, and each extra BMI unit went with about 2.9% lower testosterone in a national survey. Part of the drop is lower SHBG; the EAU explains the rest through hormones and inflammatory signals from fat tissue that quiet the brain's signal. [49], [50], [5]
• Weight change. In 2,395 EMAS men followed for 4.4 years, losing weight raised testosterone and gaining weight lowered it. Of the men who developed secondary low testosterone, 42.9% recovered, more often after weight loss (odds ratio 2.24). [51], [52]
• Type 2 diabetes. A third of 103 men with type 2 diabetes had low free testosterone, mostly with low LH and FSH, and 50% of men with both obesity and diabetes did in a larger study. [53], [54]
• Sleep apnea. It is linked with low testosterone, but treating it with CPAP has not been shown to raise testosterone (a pooled change of 1.08 nmol/L, too uncertain to count). Untreated severe sleep apnea is also a reason not to start testosterone. [1], [55]

Is low testosterone just part of ageing?

Partly, but less than most people think. Average testosterone falls slowly with age, and health and weight explain much of the fall.

• How fast it falls. Men aged 40–70 in the Massachusetts Male Aging Study lost about 1.6% of their total testosterone a year. In UK Biobank, total testosterone barely changed over 4.3 years in men aged 40–69, while SHBG rose and free testosterone fell. [56], [57]
• Healthy men keep their levels. The BSSM says over 80% of men keep normal testosterone into old age, and the EAU says obesity and illness drive most of the age-related fall. [6], [5]
• Low readings are not the condition. In a Baltimore study, low readings reached about 20% of men over 60 and 50% over 80. But strictly defined late-onset hypogonadism, with sexual symptoms and low total and free testosterone, affected 2.1% of EMAS men aged 40–79: 0.1% in their 40s rising to 5.1% in their 70s. [58], [7], [6]

Regulators and guidelines disagree about "age-related" low testosterone. US labels still say safety and effectiveness in "age-related hypogonadism", which the FDA describes as low testosterone "without a clear cause", have not been established. In June 2026 the FDA asked makers to remove that limitation, a request not yet in any label as of September 2026. The Endocrine Society's July 2026 statement says the diagnosis is made the same way at any age. See late-onset hypogonadism. [59], [60], [61], [4]

How common is low testosterone?

It depends on the definition: uncommon with symptoms plus low levels, common with a single blood test alone.

[7], [62], [49]

Many men with a low reading have no symptoms (47.6% of those aged 50 and older in BACH), which is why single-test figures such as "1 in 3 men" overstate the condition. [62]

Is there a "low T epidemic"?

Unsettled. One Massachusetts study found a population-wide fall that age did not explain, and US national surveys showed lower levels in young men in later years, although lab methods had changed; another analysis of the same surveys found little change. [63], [64], [65]

Can young men have low testosterone?

Yes, at any adult age, according to the BSSM. The causes to look for are Klinefelter syndrome, pituitary disease, past anabolic steroid use, opioids, obesity, and severe dieting or overtraining. [6], [39], [48], [1]

It is less common than forums suggest: among 2,130 men aged 18–40 seen for erectile dysfunction, 10.7% had low testosterone, more often with a higher BMI, depression or past cancer. For young men, fertility is usually the deciding issue in treatment (see what if you want children). Testosterone for teenagers, for example for delayed puberty, belongs only in specialist care. [66]

How is low testosterone usually treated?

By treating the cause where possible, and with testosterone therapy (TRT) when low testosterone is confirmed, causes symptoms and children are not planned soon. Men who want children are steered to medicines that keep sperm production going. This section describes the choices clinicians weigh; it is not a personal plan. [4], [5], [2], [1]

[4], [5], [20], [3], [2], [67], [68], [1]

Should the cause be treated before starting testosterone?

Most guidelines say yes for functional causes, but they disagree on whether lifestyle change alone should come first.

• Cause first. The EAU strongly recommends improving lifestyle, losing weight, stopping medicines that interfere and treating other illnesses before starting testosterone. The Endocrine Society's 2026 statement calls weight loss typically first-line when obesity (a BMI over 27) is the only cause, and the EAA recommends lifestyle change and weight loss for overweight men with functional low testosterone. [5], [4], [14]
• Both together. The BSSM says current evidence does not support lifestyle change alone as first-line treatment and recommends lifestyle change together with testosterone for men with symptoms. The AUA counsels every man on lifestyle and advises weight-loss programs alongside testosterone for men who are overweight. [6], [2]

How much does weight loss raise testosterone? Less than many hope, unless the loss is large. Pooled studies found rises of about 2.5–2.9 nmol/L (about 70–85 ng/dL) after diet-based weight loss and 7.2–8.7 nmol/L after bariatric surgery. Diet and exercise alone raise it only about 1–2 nmol/L, according to the European urology guideline, and 60–86% of lost weight is regained within three years. [69], [70], [5]

Weight-loss medicines. In a 16-week trial in men with obesity, liraglutide raised testosterone by 2.6 nmol/L with 7.9 kg of weight loss, against 5.9 nmol/L and 0.9 kg with testosterone gel. Reviews of small, short studies found rises of about 2.5–5.2 nmol/L with GLP-1 medicines, which, unlike testosterone, keep LH and FSH working. [71], [72], [73]

Opioids. For men with opioid-related low testosterone who have sexual symptoms and are unlikely to stop opioids, the Endocrine Society suggests considering testosterone. [1]

What does testosterone therapy involve?

Testosterone comes in several forms, each with its own guide:

• Injections: testosterone cypionate, testosterone enanthate (including the Xyosted autoinjector), the long-acting testosterone undecanoate injection (Aveed, Nebido), testosterone propionate and Sustanon 250.
• Skin: testosterone gel (AndroGel, Testim, Testogel, Tostran) and compounded cream.
• By mouth: oral testosterone undecanoate (Jatenzo, Kyzatrex, Tlando).
• Nasal gel: Natesto.
• Implanted pellets: testosterone pellets (Testopel).

Guidelines aim for the middle of the normal range on treatment (the AUA, for example, targets 450–600 ng/dL) and check testosterone and hematocrit at 3–6 months, at 12 months and then yearly. The TRT dosage guide covers doses, and the TRT dose calculator turns a prescribed dose into mL and syringe units. Testosterone for women uses different products and doses; see testosterone therapy for women. [2], [1]

Who should not start testosterone?

The Endocrine Society advises against testosterone for men who:

• plan to have children soon
• have breast or prostate cancer, a lump in the prostate, or a PSA above 4 ng/mL (above 3 ng/mL at high risk) without a urologist's review
• have a high hematocrit (above 48%, or 50% at high altitude, is a reason for caution), untreated severe sleep apnea or severe urinary symptoms
• have uncontrolled heart failure, had a heart attack or stroke in the last 6 months, or have an inherited clotting tendency (thrombophilia)

[1]

The AUA suggests holding off when hematocrit is above 50% until the cause is found. US labels do not allow testosterone with known or suspected prostate cancer or male breast cancer; the FDA's June 2026 request to narrow this to prostate cancer that has spread is not yet in the labels. [2], [13], [61]

What if you want children?

Testosterone therapy is the wrong choice while you are trying to conceive, because it switches off the pituitary signals the testes need to make sperm, and the labels warn that reduced fertility may not be reversible in some men. The AUA says not to prescribe it to men trying to conceive, the AUA and ASRM infertility guideline extends that to men interested in future fertility, and the EAU agrees. [3], [2], [74], [5]

Sperm usually comes back after stopping, but slowly. In contraceptive studies of 1,549 healthy men, sperm counts recovered in 67% within 6 months and in all within 24 months; recovery after years of TRT may be slower. [75], [2]

The options depend on the type. In secondary low testosterone, hCG (sometimes with FSH) can restart sperm production; in primary low testosterone it cannot, and the options are donor sperm, adoption, or sperm retrieval for IVF. The AUA allows hCG, clomiphene-type tablets (SERMs) or aromatase inhibitors to keep fertility, noting that only hCG is FDA-approved for men. The tablets are less proven: clomiphene improved sex drive less than testosterone gel in a 2026 review, and enclomiphene was refused approval in the EU in 2018 over unproven benefit and a blood-clot risk. [1], [2], [76], [67]

See TRT and fertility and hCG vs gonadorelin vs enclomiphene.

Should older men with low testosterone be treated?

Only when symptoms and repeated low levels come together, most guidelines say. The Endocrine Society suggests against routinely treating all men aged 65 and older with low levels, the EAU advises against using testosterone for vitality or strength in ageing men, and the American College of Physicians' 2020 guideline (now listed as inactive) suggested treating only sexual problems and reviewing within 12 months. US labels still carry the age-related limitation while the FDA's June 2026 request to remove it is pending (checked September 2026). [1], [5], [77], [61]

Is treatment lifelong?

For organic causes, usually yes. For functional causes, sometimes not. [1], [14]

The UK Society for Endocrinology expects lifelong therapy once the diagnosis is confirmed and rejects time-limited "trials". The AUA suggests discussing stopping 3–6 months in if testosterone is normal but symptoms have not improved, and the EAA says testosterone can be withdrawn after weight loss or when opioids can be stopped or swapped. After stopping, the body's own signal returns slowly: after two years of injections in the T4DM trial, LH and FSH recovered gradually over 12 months. See stopping TRT. [21], [2], [14], [78]

What does testosterone treatment do for low testosterone?

It helps sexual function most, gives small lifts in mood and energy, raises bone density and corrects some anemia. It did not improve memory, and the Testosterone Trials missed their main energy and walking goals. [10], [79], [80]

Most of this comes from two large controlled trials that compared testosterone with a placebo. The Testosterone Trials gave 790 men aged 65 and older with testosterone under 275 ng/dL a year of testosterone gel or placebo; 51,085 men were screened to find them. TRAVERSE randomized 5,204 men aged 45–80 with low testosterone and heart disease or high heart risk to daily testosterone gel or placebo. [79], [81]

Where the trials disagree. Erections improved in the Testosterone Trials but not in TRAVERSE, and diabetes was prevented in T4DM but not in TRAVERSE. The trials used different men, forms and programs, so neither result cancels the other; the Endocrine Society advises against using testosterone to control blood sugar. [90], [91], [1]

How long it takes. Sex drive tends to improve from about 3 weeks, erections over up to 6 months, and body composition in 12–16 weeks; the Canadian Urological Association expects changes after 3 months or more. See how long TRT takes to work and TRT and sexual health. [92], [22]

What are the risks of low testosterone and of treating it?

Is untreated low testosterone dangerous?

It is linked with a higher risk of death in observational studies, but no study has shown that low testosterone causes those deaths or that treatment prevents them.

• A 2024 analysis pooling individual data from many studies found higher death rates only at quite low levels: below 7.4 nmol/L (213 ng/dL) for death from any cause and below 5.3 nmol/L (153 ng/dL) for heart disease. An earlier review found the studies differed too much to interpret the link firmly. [93], [94]
• In EMAS (2,599 men followed for a median 4.3 years, 147 deaths), the 24 men with severe late-onset hypogonadism died at about 5 times the rate of men without it (hazard ratio 5.5, after adjusting for age, weight, smoking and general health), an association rather than proof of cause. [95]
• In TRAVERSE, deaths were similar: 144 of 2,596 men on testosterone and 148 of 2,602 on placebo (hazard ratio 0.98). [81]

Low testosterone can also go with bone loss and mild anemia. [1]

Is testosterone therapy safe for the heart?

In the largest trial, testosterone gel did not raise the combined risk of heart attack, stroke or death from heart disease compared with placebo, but it did raise some other risks, and it cannot show long-term safety or the safety of injections. TRAVERSE, in about 5,200 men with heart disease or high heart risk:

• Heart attack, stroke or death from heart disease: 7.0% on testosterone and 7.3% on placebo (182 against 190 men; hazard ratio 0.96, with a likely range of 0.78 to 1.17), meeting the trial's safety margin of 1.5. [81]
• More common on testosterone: atrial fibrillation (an irregular heart rhythm) 3.5% against 2.4%, acute kidney injury 2.3% against 1.5%, and pulmonary embolism (a clot in the lungs) 0.9% against 0.5%. [59]
• Fractures: 3.50% against 2.46%. [86]
• Prostate: high-grade prostate cancer in 0.19% against 0.12%, not a significant difference; men with a PSA above 3.0 ng/mL were excluded. [96]
• Limits: it tested only a daily gel; men used it for an average of 21.7 months; about 61% stopped their study gel early; and it enrolled only men at high heart risk. [81], [59]

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.

In February 2025 the FDA added the TRAVERSE results to all testosterone labels and removed boxed-warning language about a higher heart risk, while keeping the age-related limitation and requiring blood-pressure warnings. The remaining US boxed warnings are for Aveed (an oil reaction in the lungs and allergic reactions) and for gels and solutions (transfer to other people by skin contact). See TRT and heart health. [97], [98]

What other risks do guidelines watch?

• Red blood cells. Testosterone raises hematocrit; in T4DM, 106 of 491 men (22%) on testosterone injections passed 54%, against 6 of 484 (1%) on placebo. See hematocrit on TRT. [90]
• Fertility. See what if you want children.
• Sleep apnea. In men with obesity and severe sleep apnea, testosterone injections worsened nighttime oxygen drops at 7 weeks, though not at 18 weeks. [99]
• Prostate, estrogen and blood pressure. See TRT and the prostate, estrogen on TRT and TRT side effects.

Who should be especially cautious?

• Men with any of the conditions under who should not start, including plans for children soon, prostate or breast cancer, a high hematocrit and untreated severe sleep apnea. [1], [2]
• Men taking opioids or steroid tablets, whose low testosterone may be caused by the medicine; do not stop these on your own. [1]
• Drug-tested athletes. Testosterone is prohibited in sport at all times (see legal status). [12]
• Under-18s. Testosterone for teenagers belongs only in specialist care.
• Women. This guide is written for men; see testosterone therapy for women.

Which medicines interact with testosterone?

The US labels list four interactions:

• Insulin and other diabetes medicines. Testosterone can lower blood sugar, so diabetes medicine doses may need to come down. [59]
• Blood thinners taken by mouth, such as warfarin. Testosterone can change their effect, so clotting tests (INR) need closer checks. [59]
• Corticosteroids. Together they can increase fluid retention, a particular concern with heart, kidney or liver disease. [59]
• Medicines that also raise blood pressure, where the effects can add up. [59]

Medicines can also cause low testosterone (opioids and steroid tablets, see above) or change the blood test (high-dose biotin, see the test rules). Bring a complete list, including supplements, to a pharmacist or prescriber. Checked September 2026. [1]

Is testosterone legal, and is it allowed in sport?

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

• United States. Testosterone and its esters are Schedule III controlled substances, prescription only. [11]
• United Kingdom. Testosterone is a Class C controlled drug, in Schedule 4 Part II of the Misuse of Drugs Regulations. [100]
• Canada. Testosterone is a Schedule IV controlled substance. [101]
• Australia. Testosterone is a Schedule 4 prescription-only medicine with extra controls on possession. [102]
• Sport. The World Anti-Doping Agency (WADA) prohibits testosterone at all times. A therapeutic use exemption is granted only for organic low testosterone, not for functional causes such as ageing, obesity, overtraining or past anabolic steroid use; delayed puberty in young athletes is treated as a special case. hCG, clomiphene and aromatase inhibitors are also prohibited at all times, so a drug-tested athlete should check the exemption rules before starting any of these treatments. [12], [103]

For access, cost and coverage, see the country guides for the United States, the United Kingdom, Canada, Australia and Europe.

What do people in public communities report?

Most public posts about low testosterone come before any treatment: men with symptoms, one or two lab results and conflicting advice. The threads below are recent public Reddit discussions, read with their replies; they show what people go through, not how often it happens.

Does a repeat test change the picture?

Often. One man in his 30s had a 5 pm result with low free testosterone; a 9 am repeat two weeks later came back at 910 ng/dL. Another, with diabetes and erection problems, measured 219 and then 310 ng/dL two weeks apart, and his endocrinologist declined treatment. A man in his 20s had two low results, both drawn at 1:20 pm; replies urged a morning repeat before starting the treatment he had been prescribed. [104], [105], [106]

Finger-prick results drew the most doubt: a man training for long runs on a large calorie deficit booked a venous test after a low finger-prick result, and replies pointed at the deficit as much as the result. [107]

What is it like to be "borderline"?

Frustrating, by many accounts. A man in his 30s documented five results under 300 ng/dL over seven years, yet three endocrinologists declined treatment, citing LH and FSH in range among other reasons; replies pointed to his thyroid result and fatty liver. Another had results of 337, 283 and 365 ng/dL with a raised FSH, and his endocrinologist wanted two consecutive results under 300. Others describe years in the grey zone: one man ranged from 324 to 462 ng/dL over six years, and another from 6.8 to 11.9 nmol/L before booking a sleep study. [108], [109], [110], [111]

What causes do people find?

• Pituitary problems. A man in his 30s with a prolactin-making tumor saw prolactin fall from over 200 to 55.8 ng/mL during more than a year of cabergoline, but his testosterone was still 75 ng/dL. Another found a 3 × 2 mm pituitary lesion with normal prolactin. [112], [113]
• Sleep apnea. A man in his 20s whose CPAP reduced dangerous sleepiness at the wheel still saw testosterone fall from 244 to about 122 ng/dL. Another poster started testosterone before learning of their sleep apnea, found their breathing at night worse on it, and stopped; after starting a breathing machine they measured about 400, against 212 before, while still feeling unwell. [114], [115]
• Dieting and training. A man in his 20s lost his sex drive and morning erections during a five-month calorie deficit; his testosterone was 2.8 nmol/L and still 3.8 after he ate more, so his endocrinologist arranged a pituitary scan. Another, at 2.7 nmol/L twice with a clear MRI, was asked about repeated dieting and heavy training. [116], [117]
• Cancer treatment. After losing one testicle and having chemotherapy, a man in his 20s measured 180 ng/dL and booked a fertility appointment first. [118]
• Thyroid and weight. A man with a history of an underactive thyroid and obesity rose from about 7 to 21.9 nmol/L after weight loss and thyroid treatment, and chose monitoring over testosterone. [119]

Weight loss did not always move the number much: one man lost 8.5 kg and went from 12 to 14 nmol/L with unchanged symptoms. [120]

What happens with fertility-sparing tablets?

Numbers often rose more than symptoms improved. On prescribed enclomiphene, one man went from 327 to 991 ng/dL in 38 days, but his fatigue and brain fog stayed and his libido got worse. On clomiphene, another went from 320 to 793 in about four weeks with little change in energy or sleep. A poster whose puberty had been delayed found that hCG raised testosterone but not energy or libido, and later felt much better on testosterone injections. [121], [122], [123]

What do people report after starting testosterone?

Every direction. A man with primary low testosterone described much better mood, thinking and energy six weeks in; replies cautioned that early gains can change. Another's early improvements had largely faded by week nine, and a third found his mood better after three months but his libido and erections still poor. [124], [125], [126]

A man who started at 377 ng/dL, above every guideline line in the table above, improved his physique over a year and a half, but tiredness and low mood persisted with acne and testicular shrinkage, and he began planning a supervised exit. Another had used a testosterone solution for nearly a decade before learning he had no sperm; fertility treatment later allowed him to have a child. [127], [128]

How can you judge a low-testosterone story?

Ask: Was blood drawn in the morning, fasting, from a vein? How many tests, from which lab, and in which units? Were SHBG, free testosterone, LH, FSH and prolactin measured? What was going on at the time: weight change, a calorie deficit, heavy training, poor sleep, illness, opioids or other medicines? And what did the next test, or the next few months, show?

These selected discussions show what people experience and the questions research has not answered. They are not a survey of all men with low testosterone, a success rate or a substitute for the studies above.

What should you track?

Before a diagnosis: your symptoms, and every blood result with its date, time and fasting status. After a diagnosis: what your clinician monitors, usually testosterone and hematocrit at 3–6 months and 12 months, then yearly. Use this summary to prepare questions; it is not a personal testing plan. [1], [2]

[7], [1], [2], [49]

A single result is one point on a line: the time of day, food, illness and the lab all move the reading, so a trend of morning results drawn under similar conditions says more than any one number. The TRT blood work guide covers monitoring on treatment. [27], [29]

Common questions about low testosterone

What testosterone level is considered low?

Below about 264–300 ng/dL (9.2–10.4 nmol/L) in North American guidelines and 12 nmol/L (about 350 ng/dL) in most European ones, on at least two morning tests and only together with symptoms. [2], [1], [5] See the key numbers.

What is a normal testosterone level for a man my age?

In men without obesity, the median is about 530 ng/dL at 19–39 and about 480 ng/dL from 40 on, while the low end falls from about 267 to 218 ng/dL by the 60s. Guidelines still use one line for all adult ages. [25], [4] See levels by age.

Can you have low testosterone with a "normal" result?

Sometimes. If SHBG is high, total testosterone can look normal while free testosterone is low, so guidelines measure free testosterone when SHBG is altered or the result is borderline. Symptoms with a clearly normal morning level usually point to another cause. [1], [14] See free testosterone and SHBG.

Why does the test have to be in the morning, fasting and repeated?

Because testosterone is highest in the morning, drops after food, and varies from day to day. Afternoon levels were 20–25% lower in men aged 30–40, a glucose drink lowered testosterone by 25%, and 30% of men with one low result were normal on a repeat test. [27], [28], [1] See the test rules.

Does low testosterone cause erectile dysfunction, tiredness or weight gain?

It can contribute to all three, but only the sexual symptoms are closely tied to it. In EMAS, low desire, fewer morning erections and erectile dysfunction were the symptoms linked with low testosterone; tiredness and weight gain have many causes, and obesity itself lowers testosterone. [7], [1], [51] See the symptoms.

Can low testosterone be fixed without TRT?

Sometimes, when the cause is functional. Weight loss raises testosterone by about 2.5 nmol/L after dieting and more after bariatric surgery, and 42.9% of EMAS men with secondary low testosterone recovered, more often after losing weight. Primary low testosterone does not reverse. [70], [52], [1] See treating the cause.

Will treatment affect my fertility?

Yes, testosterone therapy switches off sperm production, and the labels warn that reduced fertility may not be reversible in some men. Men who want children soon are usually offered hCG or clomiphene-type tablets instead, depending on the type of low testosterone. [3], [2], [1] See what if you want children.

Glossary

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

Bioavailable testosterone

Free testosterone plus the testosterone loosely bound to albumin, the share tissues can use easily. It excludes testosterone bound tightly to SHBG.

Calculated free testosterone

An estimate of free testosterone worked out from total testosterone, SHBG and albumin with a formula. It agrees closely with equilibrium dialysis.

Compensated hypogonadism

Normal testosterone with a high LH, as if the pituitary is working harder to keep testosterone up. Its meaning is unclear, and it is usually watched rather than treated.

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.

CPAP

Continuous positive airway pressure: a bedside machine that blows air through a mask to keep the airway open during sleep. It is the standard treatment for obstructive sleep apnea.

Equilibrium dialysis

A reference laboratory method that measures free testosterone directly by separating it from protein-bound testosterone through a membrane.

Free androgen index (FAI)

A simple ratio of total testosterone to SHBG. It is not a reliable measure of available testosterone in men.

Free testosterone

The small share of testosterone, about 2–4%, that is not attached to any protein in the blood.

FSH (follicle-stimulating hormone)

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

GnRH (gonadotropin-releasing hormone)

The brain signal that tells the pituitary to release LH and FSH. Gonadorelin is a medicine that copies it.

Gynecomastia

Growth of breast tissue in men, often tender at first. It is linked to a higher estrogen-to-testosterone balance.

Hazard ratio

A measure comparing how often an event happens over time in two groups. A hazard ratio of 1 means no difference; 0.96 means about 4% lower in the first group.

Hematocrit

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

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.

Hypothalamus

A small area at the base of the brain that controls many hormones. It starts the testosterone signal chain by releasing GnRH.

Karyotype

A blood test that counts and checks a person's chromosomes. It diagnoses Klinefelter syndrome (47,XXY).

LC-MS/MS (mass spectrometry)

Liquid chromatography with tandem mass spectrometry, the most accurate lab method for measuring testosterone.

Leydig cells

Cells in the spaces between the testicle's tubules that make testosterone when LH reaches them.

LH (luteinizing hormone)

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

Pituitary gland

A pea-sized gland below the brain that releases LH, FSH, prolactin and other hormones.

Placebo

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

Primary hypogonadism

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

Prolactin and prolactinoma

Prolactin is a pituitary hormone; too much of it switches off the signal to the testes. A prolactinoma is a usually benign pituitary tumor that makes prolactin.

Secondary hypogonadism

Low testosterone because the brain and pituitary send too little LH and FSH to the testicles. Also called hypogonadotropic hypogonadism.

SERM (selective estrogen receptor modulator)

A tablet, such as clomiphene, enclomiphene or tamoxifen, that blocks estrogen's feedback in the brain so the pituitary releases more LH and FSH.

SHBG (sex hormone-binding globulin)

A blood protein that carries testosterone. Testosterone bound to it is not immediately available to tissues, so SHBG affects how much free testosterone there is.

Thrombophilia

An inherited or acquired tendency to form blood clots more easily than normal.

Total testosterone

All the testosterone in a blood sample, bound and free together. It is the standard first test for low testosterone.

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.

How this guide was researched

This guide is built from a thorough review of the sources cited throughout it: clinical guidelines from 12 medical bodies, product labels, published clinical trials and population studies, and regulatory documents. We also reviewed public online forums where men describe their own low-testosterone tests, causes and treatment decisions.

The guide cites 128 sources, including 59 original studies in people, 13 clinical guidelines and position statements, and 25 public community discussions. Each type of source answers a different question. Guidelines and labels show what clinicians are told to do. Trials and studies show what was measured. 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