FIB-4 uses routine blood tests to identify people who are unlikely to have advanced fibrosis and can be managed in primary care. Indeterminate results are usually followed by elastography (FibroScan) or an ELF test.
How to use the FIB-4 Calculator
- Age
- AST
- ALT
- Platelets
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter age, AST, ALT and platelet count from the same blood test.
Inputs explained
| Field | What to enter |
|---|---|
| Age | In years |
| AST | In U/L |
| ALT | In U/L |
| Platelets | In ×10⁹/L |
Example values
How the main result changes when Age changes and everything else stays at the example values above:
| Age (years) | FIB-4 |
|---|---|
| 27.5 | 0.82 |
| 41.25 | 1.23 |
| 55 | 1.64 |
| 68.75 | 2.05 |
| 82.5 | 2.46 |
| 110 | 3.28 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
FIB-4 = age × AST ÷ (platelets (×10⁹/L) × √ALT)
< 1.3 low risk (< 2.0 if age ≥ 65) · 1.3–2.67 indeterminate · > 2.67 high risk of advanced fibrosis
Worked example
Inputs — Age: 55 years; AST: 40 U/L; ALT: 45 U/L; Platelets: 200 ×10⁹/L.
Results — FIB-4 = 1.64; Risk of advanced fibrosis = Indeterminate – consider elastography.
Key terms
- Fibrosis
- Scarring of the liver.
Frequently asked questions
What is a normal FIB-4?
Below 1.3 (below 2.0 if 65 or older).
Is FIB-4 reliable under 35?
It is less accurate in young people.
What comes after an indeterminate FIB-4?
Usually transient elastography (FibroScan) or the ELF blood test.