FIB-4 Index Calculator.
FIB-4 is the first-line, non-invasive screen for advanced liver fibrosis in fatty liver disease. It needs only four routine values — age, AST, ALT, and platelets — no biopsy.
Frequently Asked Questions
What is the FIB-4 index?+
FIB-4 (Fibrosis-4) is a non-invasive score that estimates the likelihood of advanced liver fibrosis (scarring), mainly in fatty liver disease. It combines four routine values — age, AST, ALT, and platelet count — into a single number, so it screens for fibrosis without a biopsy.
How is the FIB-4 score calculated?+
FIB-4 = (age × AST) ÷ (platelets × √ALT). You only need a standard blood panel and your age. Enter those values above and the calculator returns your score and the risk band it falls into.
What are the FIB-4 cut-offs?+
For adults under 65: below 1.30 suggests low risk of advanced fibrosis, 1.30–2.67 is indeterminate, and above 2.67 suggests advanced fibrosis warranting specialist referral. For people aged 65 and older, the lower cut-off rises to 2.0 to avoid false positives, per McPherson et al. (2017).
Is FIB-4 the same as a fibrosis score?+
FIB-4 is one of the most widely used liver fibrosis scores, but not the only one — others include the NAFLD Fibrosis Score and APRI. FIB-4 is favored as a first-line screen because it uses only routine bloods and age, and it performs well at ruling out advanced fibrosis.
What should I do if my FIB-4 is high?+
A FIB-4 above the upper cut-off does not diagnose fibrosis — it flags the need for further assessment. The usual next step is a specialist referral for elastography (e.g. FibroScan) or further imaging to confirm. Bring the result to your doctor rather than acting on the number alone.
The first-line fatty-liver fibrosis screen.
Fatty liver disease (MASLD) is common and usually harmless until it scars (fibrosis). The question that matters is who has advanced fibrosis — and biopsy is invasive. FIB-4 answers it from four routine numbers: age, AST, ALT, and platelet count, combined as (age × AST) / (platelets × √ALT). Its real strength is ruling fibrosis out: below the low cut-point it has a high negative predictive value.
Interpretation has three zones — low (<1.3), indeterminate (1.3–2.67), and high (>2.67) — and the low cut-point rises to 2.0 after age 65, because FIB-4 drifts up with age and otherwise over-calls. An indeterminate or high score is a prompt for a second-line test (elastography/FibroScan or an ELF panel), not a diagnosis on its own.
- Sterling RK, Lissen E, Clumeck N, et al. (2006). Development of a simple noninvasive index to predict significant fibrosis in HIV/HCV coinfection. Hepatology, 43(6), 1317–1325.
- McPherson S, Hardy T, Dufour JF, et al. (2017). Age as a confounding factor for the accurate non-invasive diagnosis of advanced NAFLD fibrosis. Am J Gastroenterol, 112(5), 740–751.
FIB-4 flags fibrosis risk that usually tracks fatty liver — and a sustained deficit is the first-line lever. Track it.
Get the guide →For education, not medical advice. Results are estimates, not a diagnosis — discuss any abnormal value or health concern with a qualified clinician.
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