Testosterone replacement in men: monitoring, benefits and risks

Treatment is considered when symptoms and repeated low morning testosterone are confirmed, and other contributors have been addressed. It is not recommended for men with normal testosterone, for general fatigue or for age-related decline without deficiency. Men with prostate or breast cancer, uncontrolled heart failure, significant polycythaemia, untreated severe sleep apnoea or who wish to father children generally should not use it.

• Gels applied daily to the skin, which give stable levels but can transfer to others.

• Injections given at intervals by a nurse or self-administered, with different products having different intervals.

• Long-acting depot injections, usually given every few months.

• Other forms, such as patches or implants, used less commonly.

Trials show improvement in sexual desire and erectile function in men with deficiency, increases in lean mass and bone density and modest improvement in mood and energy in some. Effects build over weeks to months. Benefits are less clear in men with borderline levels. A clinician should set goals and review whether they have been achieved, stopping treatment if there is no meaningful benefit after a fair trial.

Polycythaemia, a rise in red blood cell concentration that can raise clotting risk, is the most common serious effect, which is why blood counts are checked. Other effects include acne, fluid retention, breast tenderness or enlargement, worsening of sleep apnoea, reduced testicular size and suppression of sperm production. Testosterone may stimulate growth of existing prostate cancer and can aggravate benign prostate enlargement symptoms. A large randomised trial reported in 2023 did not show an increase in major cardiovascular events in men with hypogonadism and cardiovascular risk, although questions remain about longer-term outcomes.

Typical monitoring includes a review after a few months to check levels, symptoms and haematocrit, and then at least annually. PSA and prostate examination are considered depending on age and risk, in line with guidance. Bone density may be checked if risk is high. If haematocrit rises above agreed limits, dose reduction, a change in preparation, blood donation or stopping may be needed.

Testosterone is a prescription medicine. Using products from gyms, online sellers or unregulated sources carries risks, including contamination, incorrect dosing and legal issues, and hides the need for monitoring. If you are using testosterone or anabolic steroids already, tell your doctor honestly, because it affects test results and safety, and clinicians can help without judgement.

Stopping treatment returns levels to the individual's baseline, and symptoms may return. Fertility may recover over months but not always. If you wish to conceive, discuss options with an endocrinologist or fertility specialist beforehand.