How to use it
- Enter age in years.
- Enter AST and ALT in U/L, from the same blood test.
- Enter the platelet count in 10⁹/L (the same number as 10³/µL).
- Read the FIB-4 index and the risk group.
How it works
FIB-4 = age × AST ÷ (platelets × √ALT).
| FIB-4 | Under 65 | 65 and older |
|---|---|---|
| Low risk | below 1.30 | below 2.0 |
| Indeterminate | 1.30–2.67 | 2.0–2.67 |
| High risk | above 2.67 | above 2.67 |
Worked example
A 60-year-old has AST 60 U/L, ALT 40 U/L and platelets 150 × 10⁹/L. FIB-4 = 60 × 60 ÷ (150 × √40) = 3600 ÷ 948.7 = 3.79, high risk.
A 66-year-old with AST 30, ALT 25 and platelets 200: 66 × 30 ÷ (200 × 5) = 1.98. That is low risk at 65 and over, though it would be indeterminate under 65.
Tips
- Acute hepatitis or a recent heavy drinking episode raises AST and ALT and can make FIB-4 misleadingly high.
- Low platelets from other causes (for example a blood disorder) also raise the index.
- A low score does not exclude other liver problems, only advanced fibrosis.
- This page is for information. Results should be discussed with a doctor.