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Low testosterone

Infographic of the influence of testosterone, showing what it does for the body, as described in the text.

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Testosterone is a hormone that teenage boys and men make in their testicles. They need it to develop during puberty, make sperm and develop and maintain a sex drive. It also helps them to build and maintain strong muscles and bones.

While there is naturally a reduction of testosterone with age, some boys or men have unusually low levels. This can be caused by a variety of conditions that affect the testicles' ability to make testosterone.

Low testosterone causes problems with male characteristics such as hair and muscle growth and affects sexual function. Longer term, low testosterone can increase your risk of heart disease, stroke (cardiovascular disease) and osteoporosis.

Symptoms of low testosterone

Symptoms of low testosterone vary depending on your age and how long the levels have been low.

If a boy has never had enough testosterone, they may not fully develop during puberty. They may have a lack of body hair, small testicles and smaller muscles.

Short‑term effects in adults include low sex drive, poor erections (impotence), low sperm count and breast enlargement.

Longer term, low testosterone can cause loss of body hair and muscle strength, more body fat and less energy. It can also cause thinning bones (osteoporosis).

Causes of low testosterone

Causes of low testosterone include:

Diagnosing low testosterone

Your general practice team will ask about what symptoms of low testosterone you have. They will also check the amount of body hair you have, as well as the size of your penis and testicles.

You'll need to have a blood test, to check the amount of testosterone in your blood. This test needs to be done early in the morning. If it shows a low level, you'll need a second test on another day to confirm it.

Since some medications and supplements can cause low testosterone, it's important that you tell your general practice team about any that you're taking, including gym supplements and herbal medications.

Treating low testosterone

If you need it, you'll have testosterone replacement with testosterone tablets, patches or injections.

The type and dose of the treatment varies based on your needs. The aim is to get your testosterone back to normal levels, which will help reverse symptoms. It will help with getting a deeper voice, growing a beard and pubic hair, improving sex drive and erections and strengthening muscles and bones.

Before having testosterone treatment, you'll need to have your red blood cell count checked. You'll need to have this test once a year as testosterone treatment can increase your red blood cell level.

Testosterone treatment could be dangerous if you have, or have had, prostate cancer. Your doctor will talk to you about whether you need to be checked for this or whether you need any regular monitoring.

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Written by HealthInfo clinical advisers. Last reviewed June 2023.

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Review key: HIAND-70631