Serum or plasma concentration of free testosterone (by immunoassay)

Why Is This Test Done?

Your healthcare provider may order this test to evaluate hormonal imbalances, diagnose conditions like hypogonadism (low testosterone), or assess symptoms such as low libido, fatigue, or irregular menstrual cycles in men or women. It may also be used in fertility evaluations or to monitor hormone replacement therapy.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if your lab uses a specific protocol. Wear comfortable clothing for blood draws, and inform your provider about any medications or supplements you take, as they may affect results.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The blood sample is processed into serum or plasma and sent to a lab for analysis using an immunoassay method to detect free testosterone levels.

What Are the Results Meaning?

Results are compared to reference ranges specific to your age, sex, and health status. Abnormal levels may indicate hormonal deficiencies, disorders of the adrenal or pituitary glands, or other endocrine conditions. Your provider will interpret results in the context of your overall health.