Low testosterone in men: symptoms, tests and safe treatment

Testosterone is heavily advertised, and “low T” clinics and gym supplements are everywhere. Yet many men who are told they have low testosterone do not, and many who do have a low level have a fixable cause. Getting the diagnosis right protects your health, and your fertility.

What does testosterone do?

Testosterone is the main male hormone, made mostly by the testicles under signals from the pituitary gland in the brain. It supports sex drive, erections, sperm production, muscle and bone strength, red blood cells, energy and mood.

What are the symptoms of low testosterone?

The more specific symptoms are:

• low sex drive
• fewer morning erections, or erectile problems
• breast enlargement or tenderness
• loss of body hair or less need to shave
• very small or shrinking testicles
• low sperm count or difficulty fathering a child
• hot flushes, or fractures with little injury

Less specific symptoms include tiredness, low mood, poor concentration, reduced strength and more body fat. These are common for many other reasons, so they alone do not mean your testosterone is low.

How is low testosterone diagnosed?

The Endocrine Society guideline advises that diagnosis requires both typical symptoms and a low testosterone level confirmed on at least two separate tests:

• taken early in the morning, usually before 10 am, when levels are highest
• ideally after an overnight fast, because a meal can lower testosterone
• not during an acute illness
• measured with an accurate, reliable lab method

A single low result is not enough, because testosterone varies a lot from day to day. If the total testosterone is borderline, or you have obesity or diabetes, your doctor may also check SHBG and calculate the free testosterone, because obesity lowers SHBG and can make total testosterone look low.

Your doctor will also check LH and FSH to find out whether the problem is in the testicles (primary hypogonadism) or the pituitary and brain (secondary hypogonadism). Depending on the result, they may check prolactin, iron studies, other pituitary hormones, a semen analysis, or an MRI of the pituitary.

What commonly lowers testosterone?

In practice, many cases of low testosterone are not due to diseases of the testicles but to things that suppress the pituitary signals. This is called functional hypogonadism:

• obesity, especially a large waist. Read what is obesity.
• type 2 diabetes and prediabetes. Read what prediabetes means.
• sleep apnoea and poor or short sleep
• opioid painkillers, steroid medicines and some other drugs
• heavy alcohol use
• any serious or long-term illness
• anabolic steroid use in the past, which can suppress the body’s own production for months or longer

Treating these often raises testosterone naturally. Weight loss in particular often raises testosterone.

Less common causes include Klinefelter syndrome, pituitary tumours, high prolactin, undescended testicles, injury, mumps affecting the testicles, chemotherapy and inherited conditions that delay puberty. Read early or late puberty.

When is testosterone treatment used?

For men with a confirmed diagnosis and symptoms, testosterone treatment can improve sex drive, sexual function, mood, bone density and body composition. It is available as injections and gels, and your doctor will discuss the options and monitoring.

The large TRAVERSE trial, published in 2023, found that testosterone treatment in middle-aged and older men with low testosterone and heart risk did not increase major heart events compared with placebo. It did show more atrial fibrillation, kidney injury and blood clots in the lungs in the testosterone group, so careful selection and monitoring still matter.

Treatment needs regular checks of testosterone levels, haemoglobin (red blood cell count), and in older men the prostate.

Why is unprescribed testosterone risky?

This is the most important point on this page. Testosterone from outside the body tells the brain to stop sending signals to the testicles. As a result:

• sperm production can fall sharply, sometimes to zero, and the testicles shrink. Recovery after stopping can take many months and is not guaranteed.
• haemoglobin can rise too high, thickening the blood
• acne, breast enlargement, mood changes and sleep apnoea can worsen
• products bought online or in gyms may be impure, wrongly labelled or contain other steroids

So if you hope to father a child now or in the future, testosterone is usually not the right treatment. Other treatments can raise your own testosterone while preserving fertility, which your doctor can discuss.

If you are already using testosterone or steroids without a prescription, do not be embarrassed to tell your doctor. Ask for help rather than stopping abruptly or continuing on your own, because both can cause problems.

What should I ask my doctor?

• Have my testosterone tests been done correctly, in the morning and repeated?
• Is my low level due to weight, diabetes, sleep or medicines?
• Is the problem in the testicles or the pituitary?
• How would treatment affect my fertility?

For a careful assessment, book a consultation or read who an endocrinologist is.