Testosterone

Definition

A testosterone test measures the amount of the male hormone, testosterone, in the blood. Both men and women produce this hormone.

The test described in this article measures the total amount of testosterone in the blood. Another test measures what is called "free" testosterone.

Alternative Names

Serum testosterone

How the test is performed

A blood sample is needed. For information on how this is done, see: Venipuncture

The recommended time of day to have a blood sample taken for this test is between 7 a.m. and 10 a.m. It may need to be repeated a second time.

How to prepare for the test

The health care provider may advise you to stop taking drugs that may affect the test.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test may be done if you have symptoms of abnormal male hormone (androgen) production.

In males, the testicles produce most of the testosterone in the body. Levels are most often checked to evaluate signs of low testosterone:

• In boys -- early or late puberty
• In men -- impotence, low level of sexual interest, infertility, thinning of the bones

In females, the ovaries produce most of the testosterone. Levels are most often checked to evaluate signs of higher testosterone levels:

• Decreased breast size
• Excess hair growth
• Increased size of the clitoris
• Irregular or absent menstrual periods
• Male-pattern baldness or hair thinning

Normal Values

• Male: 300 -1,000 ng/dL
• Female: 15 - 70 ng/dL

Note: ng/dL = nanograms per deciliter

The examples above are common measurements for results for these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different specimens.Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Increased testosterone levels may mean:

• Androgen resistance (resistance to the action of male hormones)
• Cancer of the ovaries
• Cancer of the testes
• Congenital adrenal hyperplasia
• Early (premature) start to puberty

Decreased production of testosterone:

• Chronic illness
• Condition in which the pituitary gland does not produce normal amounts of some or all of its hormones
• Delayed puberty
• Failure of the testicles
• Noncancerous tumor of the pituitary cells that produces too much of the hormone prolactin

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Special considerations

visHeader

References

Swerdloff RS, Wang C. The testis and male sexual function. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 242.