Key points
- Low testosterone is diagnosed only when symptoms are present and morning blood tests are low on two separate occasions. Either one alone is not enough.[1][2]
- Treat the reversible causes first: excess weight, short sleep, sleep apnoea and certain medicines.
- The TRAVERSE trial (2023) found no increase in heart attack or stroke with TRT in men with genuinely low testosterone, but small increases in atrial fibrillation, acute kidney injury and pulmonary embolism.[3]
- External testosterone suppresses sperm production. If children are still in your plans, say so before you start.
- Treatment needs regular checks: testosterone level, haematocrit, PSA and blood pressure.
What is low testosterone?
Testosterone is the main male sex hormone. It is made in the testes on signals from the hypothalamus and pituitary gland, and it supports libido, muscle mass, bone strength, red blood cell production, energy and mood.
Testosterone deficiency (male hypogonadism) means the body produces too little testosterone and this causes symptoms or signs. The American Urological Association (AUA) is explicit that both are required for the diagnosis.[1]
Two broad types of cause
- Primary (testicular): after chemotherapy or testicular radiation, testicular inflammation, or genetic conditions. Blood tests show a high LH.
- Secondary (brain or pituitary): obesity, diabetes, sleep apnoea, long-term opioid or corticosteroid use, anabolic steroid use, or a pituitary tumour. LH is low or inappropriately normal.
Symptoms worth taking seriously
Symptoms of low testosterone are non-specific. Stress, short sleep, depression and chronic illness produce many of the same complaints. The Endocrine Society groups them as follows.[2]
| More specific | Common but less specific |
|---|---|
| Reduced sex drive | Fatigue, low energy |
| Fewer morning erections | Low mood, irritability, poor concentration |
| Breast enlargement or tenderness | Loss of muscle, more abdominal fat |
| Less body hair, smaller testes | Poor sleep, hot flushes or sweats |
| Low bone density or low-trauma fracture | Mild unexplained anaemia |
The AUA also suggests testing men without symptoms who have unexplained anaemia, low bone density, diabetes, past chemotherapy or testicular radiation, HIV, long-term opioid or corticosteroid use, infertility, or pituitary disease.[1]
How to get a reliable blood test
Testosterone peaks in the morning and dips after meals, so a test at the wrong time often gives a falsely low result.
- Test in the morning, generally before 10 am, ideally fasting.[2]
- Repeat on a different day if the first result is low. A single value can mislead.[1][2]
- Use a recognised threshold. The AUA uses total testosterone below 300 ng/dL (about 10.4 nmol/L). The Endocrine Society uses the harmonised lower limit for healthy young men, 264 ng/dL (about 9.2 nmol/L).[1][2] Labs outside the US usually report in nmol/L, so check the unit on your report.
- Find the cause with LH (and FSH). If LH is low or normal, prolactin may be checked to look for a pituitary problem.[1]
- Baseline safety tests before treatment: haematocrit, and PSA in men aged 40 and over.[1]
Before medication: fix what can be fixed
In many working-age men, lower testosterone tracks with weight, sleep and medication, all of which can change. The AUA recommends lifestyle counselling for every man with testosterone deficiency as part of treatment.[1]
- Lose weight, especially abdominal fat.
- Prioritise sleep and get screened for sleep apnoea if you snore loudly, wake gasping or feel sleepy during the day.
- Review medicines such as opioid painkillers and steroids, and stop anabolic steroids.
- Manage related conditions such as diabetes and high blood pressure, and cut back on alcohol.
Testosterone replacement therapy (TRT)
Once the diagnosis is clear and reversible factors have been addressed, TRT may be considered. The goal is a level in the middle of the normal range, which the AUA puts at 450–600 ng/dL (about 15.6–20.8 nmol/L)[1], not the highest number possible.
| Form | How it is used | Worth knowing |
|---|---|---|
| Gel | Applied daily | Steady levels; avoid skin contact with partners and children after applying |
| Short-acting injection | Every 1–2 weeks | Low cost; levels peak and dip, and high haematocrit is more common |
| Long-acting injection | Every 10–14 weeks after loading doses | Convenient; given by a health professional |
| Oral capsules | Twice daily with food | Must be taken with a meal containing fat to be absorbed |
Product availability differs between countries. The AUA recommends licensed, commercially manufactured products rather than compounded or unregulated testosterone.[1]
If you want children
External testosterone tells the brain to reduce LH and FSH, so sperm production falls and can stop altogether (see the diagram above). The AUA advises that men who want to preserve fertility should not use TRT; alternatives that stimulate your own production, such as SERMs, hCG or aromatase inhibitors, may be used instead.[1]
How safe is it? The TRAVERSE trial and updated drug labels
Cardiovascular safety has been the central question about TRT for a decade. TRAVERSE, published in the New England Journal of Medicine in 2023, randomised 5,246 men aged 45–80 with low testosterone and existing cardiovascular disease or high cardiovascular risk to testosterone gel or placebo gel, with mean follow-up of about 33 months.[3]
| Outcome | TRT | Placebo |
|---|---|---|
| Major adverse cardiac events (cardiovascular death, heart attack, stroke) | 7.0% | 7.3% |
| Atrial fibrillation | 3.5% | 2.4% |
| Acute kidney injury | 2.3% | 1.5% |
| Pulmonary embolism | 0.9% | 0.5% |
On 28 February 2025 the US Food and Drug Administration (FDA) removed the boxed warning about cardiovascular risk from all testosterone products, while adding a class-wide warning that testosterone can raise blood pressure.[4] In June 2026 the US Department of Health and Human Services requested further label updates, including on age-related hypogonadism and prostate warnings, while keeping recommendations for prostate risk assessment and monitoring.[5] These are US regulatory decisions; labelling in Europe, Thailand and elsewhere may differ.
Other side effects to monitor
- Raised haematocrit (erythrocytosis): the most common issue. Above 54%, the dose is reduced, the formulation changed or treatment paused.[1][2]
- Higher blood pressure: check it at every follow-up visit.[4]
- Acne, oily skin, breast enlargement, and possible worsening of sleep apnoea.
- Smaller testes and lower sperm count, as explained above.
Who should avoid it or take extra care
The Endocrine Society advises against starting TRT in men planning a pregnancy soon, with breast or prostate cancer, a palpable prostate nodule or unevaluated raised PSA, haematocrit above 50% at baseline, untreated severe sleep apnoea, uncontrolled heart failure, or a heart attack or stroke within the last 6 months.[2] A history of blood clots needs careful discussion before starting.
Monitoring during treatment
| Check | Typical schedule |
|---|---|
| Symptoms and testosterone level | About 3–6 months after starting, then every 6–12 months[1][2] |
| Haematocrit | Baseline, 3–6 months, then yearly[2] |
| PSA and prostate assessment | Baseline at age 40+, at 3–12 months, then per screening guidance[1][2] |
| Blood pressure | Every visit[4] |
If symptoms have not improved after 3–6 months despite a level in the target range, the Endocrine Society recommends stopping and looking for other causes.[2]
How we care for you at Dr. Kris Clinic
- Private one-to-one consultation with the physician, in English or Thai: symptoms, sleep, medicines, fertility plans and a physical examination.
- Correctly timed blood tests, repeated to confirm, plus tests for the cause and baseline safety.
- A shared decision on benefits, risks and alternatives, including options that do not involve hormones.
- Ongoing follow-up for levels, haematocrit and blood pressure, with dose changes, or stopping if treatment is not helping.
Frequently asked questions
Does testosterone therapy cause prostate cancer?
Available trial and observational data have not shown a clear increase in prostate cancer with TRT, but long-term uncertainty remains. Men aged 40 and over should have a PSA before starting and prostate monitoring during treatment.[1][5]
Once I start TRT, is it for life?
Not necessarily. When low testosterone is driven by reversible factors such as excess weight, poor sleep or certain medicines, levels can recover. Permanent testicular or pituitary causes usually need long-term treatment. Stopping should be planned with your doctor.
Will TRT fix erectile dysfunction?
In older men with confirmed low testosterone, TRT modestly improves libido and sexual activity, with a smaller effect on erections.[6] Erectile dysfunction usually needs PDE5 inhibitor treatment and attention to vascular health.
Can I still have children if I take testosterone?
External testosterone suppresses sperm production. If you may want children, tell your doctor before starting, as there are alternative treatments that preserve fertility.[1]
I am already on TRT and staying in Thailand. Can I continue treatment?
Bring your prescription details and recent blood results. A physician will review your regimen and monitoring needs; testosterone is prescription-only in Thailand and is prescribed only after a medical assessment.
Concerned about your hormones or energy?
Confidential, one-to-one care in Surat Thani, the mainland gateway to Koh Samui, Koh Phangan and Koh Tao. Tue–Fri 17:00–20:00 · Sat–Sun 10:00–15:00 (Thailand time, UTC+7)
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Dr. Krida Uakridathikarn, MD (Dr. Kris)
Board-certified family physician with certificate training in clinical sexology and sexual medicine. He works at Suratthani Hospital, including its Medical Education Center, and provides sexual health, hormone and LGBTQ+ inclusive care at Dr. Kris Clinic. Profile and CV
References
- Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and management of testosterone deficiency: AUA guideline. J Urol. 2018;200(2):423–432 (reviewed and validity confirmed 2024). auanet.org
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744. endocrine.org
- Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular safety of testosterone-replacement therapy (TRAVERSE). N Engl J Med. 2023;389(2):107–117. doi:10.1056/NEJMoa2215025
- U.S. Food and Drug Administration. FDA issues class-wide labeling changes for testosterone products. 28 Feb 2025. fda.gov
- U.S. Department of Health and Human Services. HHS announces requested updates to testosterone therapy product labels. 18 Jun 2026. hhs.gov
- Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of testosterone treatment in older men (Testosterone Trials). N Engl J Med. 2016;374(7):611–624. doi:10.1056/NEJMoa1506119
Related reading
This article is for general education and is not personal medical advice or a promise of results. Diagnosis and treatment require assessment by a doctor. Content reflects clinical guidelines as of the last review date.