TRT replaces testosterone that the body is not making in adequate amounts. It is a treatment for hypogonadism, meaning symptoms plus consistently low levels, not a general tonic for ageing or a performance enhancer. The Endocrine Society recommends it for men with symptomatic testosterone deficiency after a proper discussion of benefits, risks and monitoring.1
It comes in several forms, including gels applied to the skin, injections and other preparations. Whatever the form, the guideline suggests aiming for testosterone levels in the mid-normal range during treatment.1 Because testosterone from outside the body switches off the brain's signals to the testes, TRT reduces the testes' own output of testosterone and sperm.
Who is TRT for?
Men with symptoms of testosterone deficiency and unequivocally, consistently low testosterone on repeat morning tests.1 The guideline advises against starting it in several situations, including men planning to father a child soon.
Before starting, a doctor should look for the cause of the low level and check for reasons not to treat, and there should be a frank conversation about what TRT can and cannot do.1 Men with normal testosterone who simply feel tired or older are not who it is designed for: the guideline recommends it for confirmed, symptomatic deficiency only.1
- Planning fertility in the near term1
- Breast or prostate cancer, or a prostate nodule or raised PSA without urology review1
- Raised haematocrit (thick blood)1
- Untreated severe obstructive sleep apnoea1
- Heart attack or stroke in the last six months, uncontrolled heart failure or a clotting disorder1
What does TRT actually improve?
Sexual function most reliably. In the Testosterone Trials, 790 men aged 65 or over with low testosterone and symptoms who used testosterone gel for a year reported more sexual activity, more desire and better erections than those on placebo.2
The same trials found a small benefit for mood and depressive symptoms, but no benefit for vitality, and walking distance improved only when all participants were pooled.2 So TRT is not an energy tonic. Our pieces on testosterone and sex drive and testosterone after 40 put this in context.
Is TRT safe for the heart?
The largest trial so far was reassuring. TRAVERSE followed 5,246 men aged 45 to 80 with, or at high risk of, heart disease; major heart events occurred in 7.0% on testosterone gel and 7.3% on placebo.3
That met the trial's test for being no worse than placebo. However, atrial fibrillation, acute kidney injury and pulmonary embolism were more common in the testosterone group.3 The guideline recommends monitoring symptoms, testosterone levels, haematocrit and prostate cancer risk, particularly during the first year.1
Does TRT affect fertility?
Yes. Testosterone therapy suppresses sperm production, which is why it has been studied as a male contraceptive and why guidelines advise against it for men planning to conceive soon.1
The good news is that the effect usually reverses. Pooled data from 1,549 healthy men in hormonal contraception studies found sperm concentration recovered to 20 million per millilitre in 67% within six months, 90% within a year and all men within two years of stopping.4 Those were healthy volunteers, so long-term TRT users may recover more slowly. If children are in your plans, raise it before starting; see also our sperm regeneration timeline.
Common questions
Is TRT for life?
Often it is long-term, because stopping usually lets levels fall back to where they were. That is not always true for secondary hypogonadism with a fixable cause. The guideline stresses involving the patient in decisions about starting and continuing.1
Does TRT cause prostate cancer?
TRT is not given to men with prostate cancer, and guidelines call for prostate cancer risk to be assessed before and during the first year of treatment.1 Report any new urinary symptoms to your doctor.
Is it safe to use testosterone without a prescription?
No. Unprescribed testosterone skips the diagnosis, safety checks and monitoring that guidelines require, including blood counts and prostate checks.1 It will also suppress sperm production. If you think your levels are low, start with a GP and proper morning blood tests.
Read more on this
How testosterone changes after 40 (and what actually helps)
Does testosterone affect sex drive? Separating myth from mechanism
How long does it take sperm to regenerate?
Sources
- Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. PubMed
- Snyder PJ, et al. Effects of testosterone treatment in older men. N Engl J Med. 2016;374(7):611-624. PubMed
- Lincoff AM, et al. Cardiovascular safety of testosterone-replacement therapy. N Engl J Med. 2023;389(2):107-117. PubMed
- Liu PY, et al. Rate, extent, and modifiers of spermatogenic recovery after hormonal male contraception: an integrated analysis. Lancet. 2006;367(9520):1412-1420. PubMed
Not medical advice. Written by Eric Stephens from the research cited above; not reviewed by a doctor. If something worries you, see a GP.