What is a testosterone levels test?

Testosterone is the main sex hormone in males. During a boy's puberty, testosterone causes the growth of body hair, muscle development, and deepening of the voice. In adult men, it controls sex drive, maintains muscle mass, and helps make sperm. Women also have testosterone in their bodies, but in much smaller amounts.

This test measures the levels of testosterone in your blood. Most of the testosterone in the blood is attached to proteins. Testosterone that is not attached to a protein is called free testosterone. There are two main types of testosterone tests:

Total testosterone, which measures both attached and free testosterone. Free testosterone, which measures just free testosterone. Free testosterone can give more information about certain medical conditions. Testosterone levels that are too low (low T) or too high (high T) can cause health problems in both men and women.

Other names: serum testosterone, total testosterone, free testosterone, bioavailable testosterone

What is it used for?

A testosterone levels test may be used to diagnose several conditions, including:

• Decreased sex drive in men and women
• Infertility in men and women
• Erectile dysfunction in men
• Tumors of testicles in men
• Early or delayed puberty in boys
• Excess body hair growth and development of masculine features in women
• Irregular menstrual periods in women

Why do I need a testosterone levels test?

You may need this test if you have symptoms of abnormal testosterone levels. For adult men, it's mostly ordered if there are symptoms of low T levels. For women, it's mostly ordered if there are symptoms of high T levels.

Symptoms of low T levels in men include:

• Low sex drive
• Difficulty getting an erection
• Development of breast tissue
• Fertility problems
• Hair loss
• Weak bones
• Loss of muscle mass

Symptoms of high T levels in women include:

• Excess body and facial hair growth
• Deepening of voice
• Menstrual irregularities
• Acne
• Weight gain

Boys may also need a testosterone levels test. In boys, delayed puberty can be a symptom of low T, while early puberty may be a symptom of high T.

What happens during a testosterone levels test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a testosterone levels test.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruise at the spot where the needle was put in, but most symptoms go away quickly.