FIB-4 Calculator for Liver Fibrosis

Estimate advanced liver fibrosis risk in fatty liver disease from age, AST, ALT and platelets.

By Dr Amer Sheikh, GP Updated 17 October 2026 Clinical review pending

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FIB-4 formula

FIB-4 = (age × AST) ÷ (platelets × √ALT)

Interpretation

FIB-4	Next step
Below 1.3 (below 2.0 if 65 or over)	Advanced fibrosis unlikely: reassess in about 3 years
1.3 to 3.25	Indeterminate: ELF test or FibroScan
Above 3.25	Advanced fibrosis likely: refer to hepatology

FIB-4 is less accurate under 35. If your lab reports ALT only, ask for AST on the same sample.

Frequently asked questions

What is a normal FIB-4 score?

Below 1.3 (or below 2.0 from age 65) means advanced fibrosis is unlikely.

What if FIB-4 is indeterminate?

Arrange an ELF blood test or transient elastography (FibroScan), as per your local pathway.

Who should have a FIB-4?

Adults with fatty liver disease or risk factors such as type 2 diabetes and obesity.

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References

Sterling RK, Lissen E, Clumeck N, et al. Development of a simple noninvasive index to predict significant fibrosis. Hepatology 2006;43(6):1317–25.
NICE. Non-alcoholic fatty liver disease (NAFLD): assessment and management. NG49. nice.org.uk/guidance/ng49

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