FAI
A calculated index of free androgen status — total testosterone divided by SHBG.
What is it
The Free Androgen Index is calculated by dividing total testosterone (in nmol/L) by SHBG and multiplying by 100. It provides a simple proxy for androgen bioavailability.
Why it's measured
FAI has been used in clinical research, particularly in women's health and PCOS evaluation.
Reference range
Standard laboratory reference
Men: 35 – 95 / Women: < 5 index
Reference ranges vary by laboratory. Your individual reference range will appear on your test report and should be interpreted by your physician in the context of your overall health profile.
What results may indicate
Elevated
In women, has been associated with PCOS and androgen excess in research literature.
Lower
May reflect reduced androgen bioavailability — clinical context required.
These associations are general. They are not a personal diagnosis or prediction. Discuss your individual results with your physician in the context of your full health profile.
When it's measured
Calculated from total testosterone and SHBG.
Related markers
Measured in
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