What is a testosterone levels test?

A testosterone levels test measures the amount of the hormone testosterone in a sample of your blood. Hormones are chemical messengers in your bloodstream that control the actions of certain cells or organs.

Though often considered a male sex hormone, testosterone is present in females in smaller amounts. In both sexes, testosterone helps control your sex drive and helps with muscle and bone growth. In males, it is also involved in

• Body hair growth.
• A deepening voice during puberty.
• The production of sperm.
• The making of new red blood cells.
• An increase in height.

All the testosterone in your blood is either bound to proteins or unbound (free). Free testosterone is more available for your body to use when building bones and muscles. However, most of your testosterone is bound to proteins such as sex-hormone-binding globulin (SHBG) and albumin. When testosterone is bound, your body can't use it as easily. This is necessary for your health. Having most of your testosterone bound to proteins makes sure your body doesn't use too much.

Your health care provider can measure your testosterone levels by ordering one of three tests. These are:

• A total testosterone test, which measures both bound and free testosterone. This is the most common type of test.
• A free testosterone test, which measures only the unattached form of testosterone. This test is less common, but it may help your provider diagnose certain medical conditions.
• A bioavailable testosterone test, which measures free testosterone and testosterone that's attached to proteins other than SHBG. This test isn't commonly done, but like a free testosterone test, it may help diagnose certain medical conditions.

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

What is it used for?

A testosterone levels test may be used with other tests to help your provider find the cause of abnormal testosterone levels. It can also be used to monitor your health if you:

• Have had an abnormal testosterone test result in your past.
• Are taking medicine that may affect your testosterone levels.
• Are taking hormone therapy.

In children and teens, your provider may use a testosterone levels test to figure out what's causing early or delayed puberty.

Why do I need a testosterone levels test?

You may need this test if you have symptoms of abnormal testosterone levels.

For males who have gone through puberty, the test is mostly used for symptoms of low T levels (testosterone levels which are too low).

The symptoms of low T may include:

• Low sex drive.
• Erectile disfunction or "ED" (difficulty getting or keeping an erection).
• Infertility (difficulty getting someone pregnant).
• Enlarged breasts.
• Lack of face or body hair.
• Thinning bones or anemia without a known cause.
• Loss of muscle mass.

For females, the test is mostly used for symptoms of high T levels.

Symptoms of high T may include:

• Abnormal hair growth on the body or face.
• Hair loss on the head that may be like male-pattern baldness (hair loss at the temples and balding on the top of the head).
• Voice changes.
• Irregular or no menstrual periods.
• Infertility (difficulty getting pregnant).
• Acne.

What happens during a testosterone levels test?

Most testosterone levels tests involve a blood draw in a medical setting. Your provider will take a blood sample in the morning, between 7 and 10. During these hours, your testosterone levels are typically the highest.

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.

You may be able to test your testosterone levels with an at-home kit. These have everything you need to collect a blood or saliva (spit) sample to send to a lab for testing. Talk to your provider if you think an at-home test is right for you. If you do a home test, be sure to follow your provider's instructions for collecting the sample and for returning the kit for testing.

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

In certain cases, you may need to fast (not eat or drink) for several hours before the test. You may also need to stop taking certain medicines before this test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to. Ask your provider how you should prepare 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 bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

A testosterone level test alone can't diagnose any health conditions, but abnormal results with symptoms may be a sign of a health problem.

• In males, low T levels may be caused by different conditions, including:
  • Problems with the testicles (the part of the male reproductive system that makes sperm), which are the main producers of testosterone in males.
  • Chronic (long-lasting) diseases such as liver, or kidney disease.
  • A pituitary gland disorder.
  • Benign tumors (not cancer).
  • Injury to the testicles.
  • Alcohol use disorder (AUD).
  • Certain genetic diseases such as Klinefelter syndrome.
• In females low T levels are normal, but extremely low levels may be a sign of:
  • An adrenal gland disorder.
  • A pituitary gland disorder.
  • A disorder of the ovaries (the part of the female reproductive system that makes eggs).
• In males, high T levels may be caused by:
  • A tumor in the testicles.
  • Steroid use.
  • An adrenal gland disorder, such as congenital adrenal hyperplasia (CAH).
• In females, high T levels may be caused by:
  • Polycystic ovary syndrome (PCOS).
  • Ovarian cancer or other problems with the ovaries.
  • An adrenal gland disorder, such as congenital adrenal hyperplasia (CAH).
  • A disorder of the pituitary gland.

Your test results may mean different things depending on which test was done, your age, your symptoms, the results of other tests, and other conditions you may have. If your results are not normal, it doesn't always mean you have a medical condition that needs treatment. It's normal for testosterone levels to decrease with age. If you have questions about your results, talk to your provider.

Learn more about laboratory tests, reference ranges, and understanding results.