A testosterone test measures the amount of the male hormone, testosterone, in the blood.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

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

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.

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

In males, the testes produce most of the circulating testosterone. The hormone LH from the pituitary gland stimulates the Leydig cells in the testicles to produce testosterone.

In females, the ovaries produce most of the testosterone. The adrenal cortex produces another male hormone, called DHEAS.

Testosterone levels are used to assess:

• Early or late puberty in boys
• Impotence and infertility in men
• Excess hair growth, male body characteristics (virilization), and irregular menstrual periods in women

• Male: 300 -1,000 ng/dL
• Female: 20 - 80 ng/dL

Note: ng/dL = nanograms per deciliter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Increased production of testosterone:

• Androgen resistance
• Congenital adrenal hyperplasia
• Ovarian cancer
• Polycystic ovary disease
• Precocious puberty
• Testicular cancer

Decreased production of testosterone:

• Chronic illness
• Delayed puberty
• Hypopituitarism
• Prolactinoma
• Testicular failure

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)

More sensitive tests can not only measure the total amount of testosterone in the blood, but can also determine how much of that total amount is "free" or "bioavailable" testosterone.