Calculators
Free Androgen Index Calculator (FAI)
"The Free Androgen Index (FAI) is a calculation that shows how much of the testosterone in your blood is \"free\" (biologically active). It is used to assess hyperandrogenism (excess male hormone), one of the diagnostic criteria for PCOS."
Free Androgen Index Calculator (FAI)
Enter your total testosterone and SHBG values to calculate.
The FAI reference range in women varies significantly by laboratory; some laboratories consider values above 5 high, others above 6–7.
Important notice
This tool is for informational purposes only; it is not a medical diagnostic tool. Results never replace a doctor's advice or a definitive diagnosis. Laboratory reference ranges can vary by laboratory and method; always review your result together with your doctor and the reference range used by the laboratory that performed the test.
"How is FAI calculated?"
"FAI = (total testosterone [nmol/L] × 100) / SHBG [nmol/L]. If testosterone is in ng/dL, it is converted to nmol/L (nmol/L = ng/dL × 0,0347)."
Frequently Asked Questions
Why is FAI calculated using SHBG?
Most of the testosterone in the blood is bound to SHBG; only a small portion is free and active. Total testosterone alone may not provide sufficient information.
Does a high FAI always mean PCOS?
No. It does not establish a diagnosis on its own; it is assessed together with clinical findings (menstrual irregularity, acne, excess hair growth) and other criteria (the Rotterdam criteria).
References
- A critical evaluation of simple methods for the estimation of free testosterone in serum. Vermeulen A, et al. The Journal of Clinical Endocrinology and Metabolism, 1999.
- Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Teede HJ, et al. The Journal of Clinical Endocrinology and Metabolism, 2023.
Medically reviewed by Op. Dr. Şükrü Sanus, Obstetrician & Gynecologist · Last medical review: