Free testosterone (serum/plasma mass concentration)

Why This Test Is Done

Doctors may order a free testosterone test to evaluate symptoms related to hormone imbalances, such as low libido, fatigue, or changes in hair growth. It’s also used in diagnosing conditions like hypogonadism (low testosterone) or evaluating hormone therapy responses. Some cases may include monitoring conditions like polycystic ovary syndrome (PCOS) or evaluating fertility.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your blood is collected early in the morning. Wear a comfortable shirt for easy access to your arm. If you’re on hormone medications, discuss them with your provider beforehand to avoid potential interference.

What the Results Mean

Results are interpreted based on your age, sex, and overall health. While reference ranges vary by lab, lower-than-expected levels may indicate hormone deficiencies, while higher levels could signal conditions like Cushing’s syndrome or tumors. Your doctor will compare your results to your clinical picture and other tests.

Common Conditions Affecting Results

Factors like obesity, certain medications (e.g., steroids), liver disease, or stress can influence free testosterone levels. Chronic illnesses or hormonal imbalances (e.g., thyroid disorders) may also impact results. If you suspect an underlying condition, discuss symptoms with your provider.