A calculated index of androgen activity from total testosterone and SHBG.
What it is
Free androgen index (FAI) is typically total testosterone divided by SHBG (×100 in some formulae). It is a calculated aid, not a direct hormone level.
Why it matters
Used in some pathways for androgen excess or deficiency patterns alongside clinical signs.
This guide is educational only and cannot diagnose you. Discuss results, especially anything outside your laboratory’s reference interval, or that does not match how you feel, with a GP or other appropriately qualified clinician.
How it affects the body
FAI summarises how much androgen may be biologically available relative to binding protein.
For athletes
Interpret with symptoms and total testosterone: ratio-only decisions are poor practice.
For fertility planning when you want AMH with key reproductive and thyroid markers in one private panel. AMH does not predict natural conception chances.
