Serum or plasma concentration of free (unbound) testosterone

Why This Test Matters

Your body uses testosterone for important functions like muscle and bone health, sex drive, and red blood cell production. Free testosterone is particularly important because it’s the form that actively supports these processes. Levels can vary based on age, sex, and health status, so this test helps doctors diagnose or monitor conditions like hormonal imbalances, infertility, or certain cancers.

How the Test Works

Blood is drawn from a vein, usually in your arm. The sample is then processed to separate the free testosterone from protein-bound forms. Advanced lab techniques (such as immunoassay or chromatography) measure the concentration of free testosterone in your serum or plasma.

Sample Preparation and Testing Process

No special preparation is needed for this test, but you may be asked to avoid certain medications or supplements that could affect results. The test is typically done on a small blood sample collected in a tube. Results are usually available within 1–3 business days.

What to Expect Before the Test

You may feel slight discomfort during the blood draw, but it usually lasts only a few minutes. Avoid heavy exercise, smoking, or caffeine for a few hours before testing, as these can temporarily affect hormone levels.