Free Testosterone Blood 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. High or low testosterone can signal a problem in both men and women.

According to recent guidelines from the American Urological Association (AUA), the normal range in most laboratories is 300 to 800 ng/dL is normal for a man. A man with a testosterone level below 300 ng/dL should be diagnosed with low testosterone.

In women, normal testosterone levels range from 15 to 70 nanograms per deciliter (ng/dL) of blood. Testosterone levels lower than 15 ng/dL may cause: changes in breast tissue.

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 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.