Testosterone Test and Interpreting Results

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. Much of the testosterone in the blood is bound to a protein called sex hormone binding globulin (SHBG). Another blood test can measure the "free" testosterone. However, this type of test is often not very accurate.

Alternative Names: Serum testosterone

How the Test is Performed

A blood sample is taken from a vein. The best time for the blood sample to be taken is between 7 a.m. and 10 a.m. A second sample is often needed to confirm a result that is lower than expected.

How to Prepare for the Test

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

How the Test will Feel

You may feel a slight prick or sting when the needle is inserted. There may be some throbbing afterward.

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 abnormal testosterone such as:

• Early or late puberty (in boys)
• Infertility, erectile dysfunction,
• low level of sexual interest
• thinning of the bones, infertility, (in men)

In females, the ovaries produce most of the testosterone. The adrenal glands can also produce too much of other androgens that are converted to testosterone. Levels are most often checked to evaluate signs of higher testosterone levels, such as:

• Acne, oily skin
• Change in voice
• Decreased breast size
• Excess hair growth (thick, dark hair in the area of the moustache, beard, sideburns, chest, buttocks, inner thighs)
• Increased size of the clitoris
• Irregular or absent menstrual periods
• Male-pattern baldness or hair thinning

Normal Results

Normal measurements for these tests:

• Male: 300 to 1,000 ng/dL
• Female: 15 to 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 provider about the meaning of your specific test results.

What Abnormal Results Mean

Certain health conditions, medicines, or injury can lead to low testosterone. Testosterone level also naturally drops with age. Low testosterone can affect sex drive, mood, and the body in men.

Decreased total testosterone may be due to:

• Chronic illness
• The pituitary gland does not produce normal amounts of some or all of its hormones
• Problem with areas of the brain that control hormones
• Low thyroid function
• Delayed puberty
• Diseases of the testicles (trauma, cancer, infection, immune)
• Benign tumor of the pituitary cells that produce too much of the hormone prolactin
• Too much body fat (obesity)

Increased total testosterone level may be due to:

• Resistance to the action of male hormones (androgen resistance)
• Tumor of the ovaries
• Cancer of the testes
• Congenital adrenal hyperplasia
• Taking medications or drugs that increase testosterone level

References

Rosenfield RL, Barnes RB, Ehrmann DA. Hyperandrogenism, hirsuitism, and polycystic ovary syndrome. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 133.

Swerdloff RS, Wang C. The testis and male sexual function. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 234.

Free Testosterone - What is It and How Do They Test?

Does this test have other names?

• Free T-index
• What is this test?

This test measures the amount of unattached, or "free," testosterone in your blood.

Testosterone is a male sex hormone (androgen) that helps male features develop. Testosterone is made in the testes and the adrenal glands. It causes the changes that occur in boys during puberty. Testosterone helps hair and muscles grow. It also helps the penis and testes grow. Testosterone also causes a boy's voice to deepen. Men continue to make testosterone. It boosts sex drive and helps make sperm.

Women's ovaries also make small amounts of testosterone. It helps many organs and body processes in women.

The pituitary gland in your brain regulates the amount of testosterone your body makes.

Most of the testosterone in your blood attaches to two proteins: albumin and sex hormone binding globulin (SHBG). Some testosterone is not attached to proteins, or free. Free testosterone and albumin-bound testosterone are also referred to as bioavailable testosterone. This is the testosterone that is easily used by your body.

If your healthcare provider suspects that you have low or high testosterone, he or she will first test total testosterone levels. This looks at all three parts of testosterone. The free testosterone can help give more information when total testosterone is low.

Both men and women can have health problems because of low or high levels of testosterone. Women with high levels of testosterone may have polycystic ovary syndrome (PCOS). This condition marked by infertility, lack of menstruation, acne, obesity, blood sugar problems, and extra hair growth, especially on the face.

Men with low levels of testosterone (hypogonadism) can lose their sex drive, have low energy, suffer bone loss, or become infertile. Testosterone levels in men drop as they age, but this not considered to be hypogonadism. The FDA currently recommends against treating men with low testosterone caused only by aging.

Why do I need this test?

You may have this test to find out whether a low sex drive is caused by a low level of testosterone. In recent years, healthcare providers have used testosterone therapy to treat both men and women with low sex drives.

The test is also ordered for men with andropause, or late-onset hypogonadism, a condition caused by decreased testosterone. Men with this condition may have:

• Anemia
• Depression
• Decreased bone density
• Lack of energy or fatigue
• Loss of muscle mass
• Poor concentration
• Erectile dysfunction or inability to have an orgasm
• Infertility

Men with HIV/AIDS may also have low testosterone levels.

Signs and symptoms of high testosterone in women include:

• Irregular or nonexistent menstruation
• Excessive hair, especially on the face
• Blood sugar imbalance
• Infertility
• Thinning hair

If you are a man and this test reveals your free testosterone is lower than normal, your health care provider may prescribe testosterone therapy. The FDA has not approved any testosterone drugs for women.

What other tests might I have along with this test?

Men may have other tests, including:

• Luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and prolactin. These are all hormones produced by the pituitary gland.
• Sperm analysis. This test counts the number of live sperm in the liquid that a man ejaculates. This test is often used to look for an infertility problem.
• Testicular biopsy. This is a tissue sample from the testes.
• MRI of the pituitary gland

Women may have other tests, including:

• Androstenedione, total testosterone, and dehydroepiandrosterone sulfat (DHEA-S). These are other types of androgen hormones.
• LH and FSH, TSH, and prolactin. These are all hormones produced by the pituitary gland.
• Partial 21-hydroxylase deficiency evaluation. High-risk ethnic groups include Ashkenazi Jews. 

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.

Results of this test are given in picograms per milliliter (pg/mL). Your level of free testosterone is normal if it is 0.3 to 2 pg/mL, or 0.1 to 0.3 percent of your total testosterone levels.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm. This test is usually done in the morning, because testosterone levels tend to be highest at that time. But you may need to have this test more than once, and at different times of the day, to confirm low testosterone levels. This is because your testosterone level can change from morning to evening and from day to day.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Drinking excessive amounts of alcohol can affect men's hormone levels. Conditions including obesity and diabetes can also affect men's testosterone levels.

For women, having certain health conditions, such as PCOS, can increase free testosterone.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.