Low testosterone: symptoms, tests and treatment

What is low testosterone?

Low testosterone – doctors call it hypogonadism or testosterone deficiency – means the body is not making enough testosterone to do its job, and this is causing symptoms. Both parts matter: a low number on its own, without symptoms, is not usually treated, and symptoms with a normal level point to another cause.

It is not the same as the gradual decline that comes with age. Testosterone falls by about 1% a year from your 30s or 40s, which on its own rarely causes problems. In the large European Male Ageing Study, only about 2% of men aged 40 to 79 met the criteria for late-onset hypogonadism – at least three sexual symptoms together with a total testosterone below 11 nmol/L and a low free testosterone.

What are the signs of low testosterone?

The symptoms most closely linked with low testosterone are sexual:

• Low sex drive (libido)
• Fewer or weaker morning erections
• Erection problems

Other physical and mental signs can include:

• Tiredness and lack of drive
• Loss of muscle mass and strength, and more body fat, particularly around the waist
• Breast tenderness or swelling (gynaecomastia)
• Less body hair and slower beard growth
• Hot flushes and sweats, if levels are very low
• Low mood, irritability and poor concentration
• Reduced fertility
• Over time, thinning bones (osteoporosis) and anaemia

None of these is specific to low testosterone. Stress, depression, poor sleep, heavy drinking, an underactive thyroid, diabetes and heart disease can all cause the same symptoms – which is exactly why a blood test is needed.

How is low testosterone diagnosed?

Your GP will ask about your symptoms, general health, mood, sleep, alcohol and any medicines, and may examine you. If low testosterone seems possible, they will arrange a blood test.

• Morning sample. Testosterone is highest in the morning, so the blood should be taken early – ideally before 11am – and preferably when you have not eaten.
• Repeated. A single result is not enough. Levels vary from day to day and drop during any illness, so a low result is repeated on a different morning.
• Other hormones. If testosterone is low, LH and FSH show whether the problem lies in the testes or the brain. SHBG (the protein that carries testosterone) is often measured so that free testosterone can be calculated, and prolactin may be checked.

Depending on the results, your GP may refer you to an endocrinologist (a hormone specialist) or a urologist for further tests.

What causes low testosterone?

Doctors divide the causes into two groups, depending on where the problem is.

• Primary hypogonadism – the testes. The testes cannot make enough testosterone even though the brain is asking them to. Causes include Klinefelter syndrome, undescended testes, injury, mumps affecting the testes, and chemotherapy or radiotherapy.
• Secondary hypogonadism – the brain. The pituitary gland or hypothalamus does not send a strong enough signal. This is the more common type in adult men, and it is often linked with obesity, type 2 diabetes, long-term opioid painkillers, anabolic steroid use, heavy drinking, serious illness and, less often, a pituitary tumour.

The link with weight works both ways: excess fat lowers testosterone, and low testosterone makes it easier to gain fat. That is why weight loss is often part of treatment. For lifestyle changes with real evidence, see How to increase testosterone naturally.

Why does low testosterone matter for your health?

Untreated, a true deficiency can lead to loss of bone density and a higher risk of fractures, anaemia, loss of muscle and reduced fertility. Low testosterone is also common in men with type 2 diabetes, obesity and heart disease. It is not always clear which comes first, but finding low testosterone is a good reason to check your blood sugar, blood pressure and cholesterol too.

How is low testosterone treated?

The first step is to treat any cause that can be changed: losing weight, managing diabetes, treating sleep apnoea, cutting down on alcohol, or reviewing medicines such as opioids. In many men with secondary hypogonadism, this is enough to bring levels back up.

If deficiency is confirmed and persists, a doctor may offer testosterone replacement therapy (TRT). It is a prescription-only medicine, usually given as a daily gel rubbed into the skin or as injections every few weeks or months. Most men notice changes in sex drive within a few weeks; effects on muscle, bone and mood take months.

TRT is not suitable for everyone, and it needs regular monitoring:

• It stops sperm production while you are taking it, so it is not used in men who want to have children – there are other treatments for them.
• It can thicken the blood (raise the red blood cell count), so blood tests are checked regularly.
• Side effects can include acne, oily skin, breast tenderness, fluid retention and worsening of untreated sleep apnoea.
• Prostate checks (a PSA blood test) are done before and during treatment.

When should you see your GP?

See your GP if you have a persistently low sex drive, erection problems or a combination of the symptoms above that is affecting your life. Erection problems are worth checking in their own right, as they can be an early warning sign of heart disease or diabetes. Get urgent advice if you have symptoms such as a severe headache with changes in your vision, which can rarely point to a problem with the pituitary gland.

For an overview of what testosterone does and what normal levels look like, see Testosterone in men. If your symptoms started in midlife, Male menopause: is it real? explains what is and is not going on.