FIB-4 Calculator

Estimate liver fibrosis risk with the FIB-4 index from age, AST, ALT and platelet count. Example: age 50, AST 40, ALT 35 and platelets 220 give a FIB-4 of 1.54, in the indeterminate zone.

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Age (years)

AST (U/L)

ALT (U/L)

Platelets (x10^9/L, same as K/uL)

How to use the FIB-4 Calculator

Enter the values in the fields.
Press Calculate to see the result with the steps shown.

Formula and method

FIB-4 = (age in years x AST) / (platelet count in 10^9/L x square root of ALT).

FIB-4 cutoffs

Score	Meaning
Below 1.3 (2.0 if 65+)	Low risk of advanced fibrosis
1.3 to 2.67	Indeterminate; further tests
Above 2.67	High risk of advanced fibrosis

Example scores

Age	AST	ALT	Platelets	FIB-4
40	25	30	250	0.73
50	40	35	220	1.54
60	60	40	150	3.80
70	35	30	200	2.24

Who it is for

FIB-4 was developed in people with HIV and hepatitis C and is widely used to triage fatty liver disease in primary care.

Limits

This calculator is for education and is not medical advice. Decisions about testing and treatment belong with a qualified clinician.

Frequently asked questions

What is a normal FIB-4?

Below 1.3 suggests low risk (below 2.0 for ages 65+).

What does a high FIB-4 mean?

Above 2.67 suggests advanced fibrosis is likely and referral is wise.

How is FIB-4 calculated?

Age x AST divided by platelets times square root of ALT.

What is next if it is indeterminate?

Often elastography (FibroScan) or an ELF test.

Does it diagnose cirrhosis?

No.

Does alcohol matter?

The score applies to many liver diseases; discuss with your clinician.

Sources

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Effortless Math Team

11 minutes ago