What is a Testosterone Test?

It checks the level of testosterone in your blood. Your doctor uses it to diagnose conditions caused by too much or too little testosterone. That’s a hormone produced in a man’s testes.

During puberty, testosterone builds a man's muscles, deepens their voice, puts hair on their chest, and makes their penis grow. Throughout a man's life, the hormone also helps produce sperm and keep up their sex drive.

Women make testosterone too, but in smaller amounts. They produce it in their ovaries. It helps maintain hormone balance and regulates other body functions.

What Does the Testosterone Test Measure?

Testosterone travels through your blood in two ways:

• Attached to the proteins albumin and sex hormone binding globulin (SHBG)
• Free -- not attached to any proteins

Usually you'll get a total testosterone test as a screening test. This measures both free and attached testosterone. To diagnose certain conditions, doctors sometimes look only at free testosterone levels.

In males, the testosterone test can help find the reason for sexual problems, like reduced sex drive or erectile dysfunction. If you’re having a hard time getting your partner pregnant, the test can tell if your blood testosterone level is low. A low testosterone level can also mean a problem with the hypothalamus or pituitary gland, which controls how much testosterone your body makes.

In females, this test can find the reason you’re missing periods, not having periods, having a hard time getting pregnant or experiencing male patterns of hair growth such as on your chest or face. Doctors can also use it to help diagnose polycystic ovary syndrome (PCOS), which causes elevated testosterone. That’s a hormone problem that can cause irregular periods and make it hard to get pregnant. Testosterone testing is part of the work-up of certain adrenal tumors.

Why Would I Get This Test?

Your doctor might order it if you have symptoms of low or high testosterone.

Symptoms of low testosterone in men include:

• Fatigue, depression, or trouble concentrating
• Hair loss
• Loss of muscle mass
• Low sex drive
• Swollen breasts
• Trouble getting or keeping an erection
• Weak bones -- called osteoporosis

Some things that cause low testosterone can also cause a low sperm count. If your sperm count is low, your doctor might order this test.

In women, they include:

• Fertility problems
• Low sex drive
• Skipped or no menstrual periods
• Vaginal dryness
• Weakened bones -- osteoporosis

Signs of high testosterone in women include:

• Acne and oily skin
• Darkened areas of skin
• Deep voice
• Enlarged clitoris
• Excess hair on the face or body
• Hair loss on the head (baldness)
• Skipped or no periods

What Happens During the Test?

It’s a simple blood test that’s usually done early in the morning, when your testosterone levels are highest. You will have a tube of blood taken from a vein in your arm or finger. Tell your doctor if you take any drugs or herbal remedies. Some medicines can affect your test results. Because testosterone levels vary from day to day and hour to hour, if a low or high level is found, the test is usually repeated.

What Can Your Results Tell Your Doctor?

They’ll let one know whether you have normal, high, or low testosterone. A normal testosterone level for you will depend on your gender and age.

Normal total testosterone results in adult men:

• Ages 19 to 49 -- 249 - 836 nanograms per deciliter (ng/dL)
• Ages 50 and older -- 193 - 740 ng/dL

Normal total testosterone results in adult women:

• Ages 19 to 49 -- 8 - 48 ng/dL
• Ages 50 and older -- 2 - 41 ng/dL

Depending on your results, you might also need one of these other tests:

• 17-hydroxyprogesterone. It detects congenital adrenal hyperplasia, which affects your production of hormones.
• Androstenedione (AD). It checks how well your adrenal glands, ovaries, or testicles work.
• Biopsy. Your doctor removes a sample of tissue from your testicles to check for cancer.
• DHEAS. It looks for problems or tumors in your adrenal glands.
• Estrogens. It measures estrogen levels, and can help diagnose infertility or menopause.
• Follicle-stimulating hormone (FSH) or luteinizing hormone (LH). They evaluate fertility in women, and puberty in girls.
• Prolactin. It diagnoses breast discharge, missing periods, infertility, or low sex drive in women.

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