Low Testosterone

Medically reviewed by David Shusterman, MD · Updated September 16, 2026

Low testosterone is real, it is common, and it is also the single most over-marketed diagnosis in men's health. Both statements are true at once, and a man trying to work out whether he has it is caught between clinics that will treat anyone who walks in and physicians who dismiss the whole subject. Our position is narrower than either: treat it when the level is genuinely low, when symptoms match, and when the causes worth correcting first have been looked for.

Testing it properly

Testosterone follows a daily rhythm and peaks in the morning, so a level drawn at four in the afternoon is not interpretable. It should be drawn in the morning, fasting is preferable, and it must be confirmed on a second separate morning before anyone is labelled. A single low reading is a reason for a second test, not a reason for a prescription.

Total testosterone alone is often not enough. Sex hormone binding globulin rises with age and falls with obesity and insulin resistance, which means a total level can look reassuring while the free fraction — the part actually available to tissue — is low, or look low while the free fraction is adequate. Where the picture is borderline or the clinical story does not match, we measure or calculate free testosterone alongside SHBG and albumin.

The rest of the panel exists to answer a different question: why is it low? LH and FSH distinguish a testicular problem from a pituitary or hypothalamic one, which changes both the treatment and how hard we look for another cause. Prolactin is checked because a prolactinoma presents exactly this way and is treatable without any testosterone. Estradiol, a complete blood count, iron studies where indicated, HbA1c, thyroid function and a PSA in men over forty complete it.

What treatment does, and does not, reliably do

Testosterone therapy in men who are genuinely hypogonadal reliably improves libido and sexual thoughts, usually improves mood and energy modestly, increases lean mass and reduces fat mass, and improves bone density. Those are the benefits worth expecting.

What it does less reliably is fix erectile dysfunction. Erections are primarily vascular and neurological; testosterone contributes to desire more than to mechanism, and a man whose erectile difficulty is arterial will be disappointed by hormone therapy alone. It does not reliably fix fatigue in men whose testosterone is normal, and it is not a treatment for depression. The large cardiovascular safety trial in middle-aged and older men with hypogonadism and cardiovascular risk did not show an excess of major cardiac events — which settled a long-running worry — but it also did not show a benefit, and it found more atrial fibrillation, more pulmonary embolism and more acute kidney injury in the treated group. Those are the terms of the trade.

Fertility — the conversation that gets skipped

Exogenous testosterone suppresses the pituitary signal that drives the testis, and sperm production falls with it. In many men it falls to zero. This is the most consequential thing about TRT and the thing most often not said clearly before the first injection. Recovery after stopping is usual but can take many months to a couple of years, and it is not guaranteed.

A man who may want children, now or later, should not start conventional testosterone without discussing it. There are alternatives that raise testosterone while preserving or even improving sperm production — clomiphene, enclomiphene, hCG, or hCG alongside testosterone — and they are a legitimate first choice rather than a consolation prize. Sperm banking before starting is cheap insurance for a man who is uncertain.

How it is given

Injections are inexpensive and effective; weekly or twice-weekly subcutaneous dosing gives steadier levels and fewer mood and energy swings than the older fortnightly intramuscular schedule. Topical gels give smooth levels but carry a genuine risk of transferring hormone to a partner or child through skin contact, which matters in a household with young children. Pellets are convenient and last months, at the cost of being impossible to adjust once placed and occasionally extruding. Oral formulations have improved but need attention to blood pressure.

Whatever the route, monitoring is not optional: testosterone level, hematocrit — because erythrocytosis is the most common genuine complication and is dose-related — PSA, and blood pressure, at three months, six months, and annually after that. A man on testosterone who is not being monitored is not being treated; he is being supplied.

What we will and will not do

We will treat men whose levels are genuinely low on two morning tests, whose symptoms fit, and who understand the fertility implications and the monitoring commitment. We will look for the correctable causes first, particularly weight and sleep apnea, because fixing those sometimes removes the need entirely. We will use fertility-sparing approaches for men who want them.

We will not start testosterone in a man with normal levels because his energy is low, and we will not treat a number without a symptom. We will not continue therapy in someone who declines monitoring. That is a narrower door than some clinics offer, and it is deliberate.