Testosterone therapy has become a midlife shorthand for energy, muscle, sex drive, and masculine decline. The biology is more specific. Testosterone matters for the brain, blood, bone, muscle, and sexual function, but treatment is meant for men with symptoms plus repeatedly low levels, not for every man who feels older than he used to.
Testosterone is a signal, not a diagnosis
Testosterone in men is produced mainly by the testes under instructions from the hypothalamus and pituitary gland. Levels vary across the day, fall with acute illness, and tend to decline modestly with age. That means a single low result can be real, misleading, or simply badly timed. The clinical question is not whether the number is lower than it was at 25. It is whether the hormonal system is failing enough to explain a pattern of symptoms.
The symptoms that matter most are not vague midlife tiredness on their own. Reduced libido, fewer spontaneous morning erections, erectile dysfunction, low bone density, anaemia, and loss of body hair can all fit the picture, but none is perfectly specific. Sleep apnoea, depression, alcohol, obesity, medicines, thyroid disease, and overtraining can produce similar complaints. That overlap is why the Endocrine Society guideline on testosterone therapy recommends diagnosing hypogonadism only when symptoms or signs are present alongside unequivocally and consistently low testosterone.
The diagnosis needs repetition
The practical detail that gets lost in private testing adverts is repetition. Testosterone should generally be checked in the morning, when levels are highest, using a reliable assay. If the result is low, it should be repeated before treatment is considered. When total testosterone sits near the lower boundary, free testosterone, sex hormone-binding globulin, luteinising hormone, and prolactin can help separate testicular failure from pituitary signalling problems or a binding-protein issue.
This is not bureaucratic caution. It changes the diagnosis. A man with repeated low morning testosterone, low libido, anaemia, and low luteinising hormone may need a different work-up from a man with one borderline afternoon result after poor sleep and a viral illness. The treatment may also differ. In younger men who want children, testosterone can suppress sperm production; raising the level from outside the body can switch off the very axis that fertility depends on.
The strongest benefits are narrower than the marketing
For men with confirmed hypogonadism, testosterone replacement can be clinically useful. The NHS describes testosterone replacement as a treatment a specialist may offer after deficiency is confirmed, usually as a gel or injection, with the aim of correcting the deficiency and relieving symptoms. That is a different claim from saying testosterone is a general midlife performance drug.
The evidence is most defensible for sexual symptoms in appropriately selected men. The American College of Physicians guideline on age-related low testosterone advises clinicians to consider testosterone in older men mainly for sexual dysfunction after a discussion of benefits, harms, costs, and patient preferences. The same guideline advises against starting testosterone to improve energy, vitality, physical function, or cognition in men with age-related low testosterone, because the evidence for those outcomes is weaker.
That distinction matters. Fatigue is real, and so is the frustration of training harder for smaller gains after 50. But a treatment can improve one domain without becoming an answer for all of them. If a man’s main problems are sleep restriction, abdominal weight gain, heavy drinking, or untreated obstructive sleep apnoea, testosterone may make the laboratory number look better while the central driver remains untouched.
TRAVERSE changed the safety conversation, not the whole decision
The cardiovascular question has been the major cloud over testosterone prescribing for more than a decade. The large TRAVERSE trial, published in the New England Journal of Medicine in 2023, enrolled more than 5,000 men with hypogonadism and pre-existing or high cardiovascular risk. Testosterone gel was non-inferior to placebo for major adverse cardiovascular events, meaning the trial did not show an excess of heart attack, stroke, or cardiovascular death under those conditions.
That finding is important, but it is not a blank cheque. TRAVERSE studied men who met entry criteria and were monitored in a trial. It did not prove that testosterone is harmless in men without true hypogonadism, nor did it settle every long-term question. The trial also reported higher rates of atrial fibrillation, acute kidney injury, and pulmonary embolism in the testosterone group, signals that deserve attention in clinical conversations.
The FDA’s 2025 class-wide labelling update reflects this mixed picture. The agency said TRAVERSE did not show increased adverse cardiovascular outcomes in men using testosterone for hypogonadism, but it also required new information about increased blood pressure across testosterone products after ambulatory blood pressure studies. In other words, the old fear of inevitable heart harm has softened; the need to monitor blood pressure and individual risk has not disappeared.
Monitoring is not optional
Testosterone treatment asks for follow-up, not just a prescription. Clinicians commonly monitor testosterone levels, symptoms, haematocrit, prostate-related risk where appropriate, blood pressure, and adverse effects. Haematocrit matters because testosterone can increase red blood cell production; if the blood becomes too concentrated, clotting risk may rise. Dose, formulation, and interval can then need adjustment.
Formulation also matters. Gels avoid injection peaks but can transfer to partners or children if skin contact occurs before the gel dries and the area is covered. Injections can be convenient but may produce peaks and troughs, depending on the ester and schedule. Oral and newer formulations carry their own safety and monitoring considerations. The compound is the same hormone; the delivery system changes the experience.
There is also a psychological dimension. Many men arrive at testosterone treatment after months or years of feeling unlike themselves. That can make any early improvement feel like proof that every previous symptom was hormonal. Sometimes it was. Often the improvement is partial. Good follow-up keeps the question open: what changed, what did not, and what else still needs attention?
What this means in practice
- Do not treat one isolated testosterone result as a diagnosis; repeat a morning test and interpret it alongside symptoms.
- Ask what else could explain the symptom pattern, especially sleep apnoea, depression, alcohol intake, obesity, medicines, and thyroid disease.
- If fertility matters, discuss it before starting treatment, because external testosterone can suppress sperm production.
- Judge treatment by specific goals, such as libido or anaemia, rather than a general promise of vitality.
- Make monitoring part of the decision from the start: haematocrit, blood pressure, prostate context, symptoms, and side effects.
- Stop and reassess if the target symptom does not improve after an adequate trial under medical supervision.
What we don’t know
We still do not have perfect answers for long-term testosterone use in men whose levels are low-normal, whose main complaint is fatigue, or whose symptoms are driven by several overlapping problems. TRAVERSE was reassuring for major cardiovascular events in a defined higher-risk population, but it does not answer every question about younger men, very long treatment duration, fertility-preserving approaches, or off-label use by men without confirmed hypogonadism.
We also do not have a simple threshold that translates neatly from a blood result to a treatment decision. Laboratories differ, free testosterone calculations vary, and symptoms do not map perfectly onto a number. That uncertainty is not a reason to ignore testosterone. It is a reason to treat it as a medical signal that needs context.
For men after 50, testosterone therapy can be valuable when the diagnosis is solid and the goals are specific. It is less convincing as an answer to ordinary ageing, poor recovery, or midlife unease. The threshold matters because the treatment is powerful enough to help, and powerful enough to deserve restraint.
Photo: Tima Miroshnichenko on Pexels.