What this marker measures
Free testosterone can be measured directly or calculated from total testosterone and SHBG. Calculated free testosterone is generally considered reliable; direct equilibrium-dialysis assays are the reference method.
High or low: what it can mean
High Free Testosterone
Elevated free testosterone in females can be associated with PCOS, congenital adrenal hyperplasia, or androgen-secreting tumours. In males, high free testosterone is uncommon unless exogenous testosterone is used.
Read full explanation →
Low Free Testosterone
Low free testosterone in males may cause low libido, fatigue, loss of muscle mass, and mood symptoms. Confirming hypogonadism usually requires repeated morning measurements together with total testosterone, LH, and FSH.
Read full explanation →
Frequently asked questions
What is Free Testosterone?
+
Free testosterone is the small fraction of testosterone not bound to SHBG or albumin — the form biologically available to tissues. It often correlates better with clinical symptoms than total testosterone, particularly when SHBG is abnormal.
What does Free Testosterone measure?
+
Free testosterone can be measured directly or calculated from total testosterone and SHBG. Calculated free testosterone is generally considered reliable; direct equilibrium-dialysis assays are the reference method.
What does high Free Testosterone mean?
+
Elevated free testosterone in females can be associated with PCOS, congenital adrenal hyperplasia, or androgen-secreting tumours. In males, high free testosterone is uncommon unless exogenous testosterone is used.
What does low Free Testosterone mean?
+
Low free testosterone in males may cause low libido, fatigue, loss of muscle mass, and mood symptoms. Confirming hypogonadism usually requires repeated morning measurements together with total testosterone, LH, and FSH.
Related biomarkers
Editorial note
LabTestly explains lab markers using plain-English educational content. Reference ranges may vary by laboratory and should be interpreted with a clinician.
Educational content · Editorially reviewed for clarity · Last updated
Common sources used for lab-test education
Not medical advice
This page is for general understanding only and does not replace medical advice from your clinician. Reference ranges can vary by laboratory, age, sex, pregnancy status, medications, and clinical context.