Free Androgen Index (FAI)
The Free Androgen Index (FAI) is a ratio used to determine the amount of biologically active testosterone. It is calculated as (Total Testosterone / SHBG) × 100. Used as a marker for androgen status…
Category: Hormones
Also known as: free androgen index
Reference range: 24–104 ratio (Source: ABIM)
Standard unit: ratio
High values may indicate
Elevated FAI may indicate excess androgen activity, potentially due to testosterone supplementation, polycystic ovary syndrome (in females), or other androgen excess conditions.
Low values may indicate
Low FAI may suggest androgen deficiency or hypogonadism.
Frequently asked questions
- What is a normal Free Androgen Index (FAI) level?
- A typical reference range for Free Androgen Index (FAI) is 24–104 ratio (source: ABIM). Reference ranges vary by laboratory, age, and sex, so always compare against the range on your own lab report.
- What units is Free Androgen Index (FAI) measured in?
- Free Androgen Index (FAI) is most commonly reported in ratio. Labs in different countries may use other units — you can convert between them with BloodId's blood test unit converter.
- Where do Free Androgen Index (FAI) reference ranges come from?
- BloodId uses ABIM standard reference ranges and educational information from MedlinePlus (see our methodology). Reference ranges still vary by lab, age, and sex, so always compare against your own report.
- Can I track Free Androgen Index (FAI) over time?
- Yes. Upload results from any lab and BloodId charts your Free Androgen Index (FAI) over time against its reference range, so you can see whether the trend is rising, falling, or stable.
Related biomarkers
Source: BloodId admin-reviewed
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