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FIB-4 Calculator

Free health calculator · FIB-4 (Fibrosis-4 Index) is a non-invasive scoring system that estimates the degree of liver fibrosis using four readily available values from standard blood tests.

Formula
(Age × AST) ÷ (Platelets × √ALT)

What is FIB-4?

FIB-4 was originally validated in HIV/HCV co-infected patients but is now widely used for screening liver fibrosis in the general population, particularly for MASLD (metabolic dysfunction-associated steatotic liver disease). A score below 1.30 has a negative predictive value of approximately 90% for excluding advanced fibrosis. Above 2.67 has a positive predictive value of 80% for detecting fibrosis.

FIB-4 and longevity

The liver is the central metabolic organ. FIB-4 provides a free, non-invasive window into liver health using values already on a standard blood panel (AST, ALT, platelets). With MASLD affecting 1 in 4 adults, routine FIB-4 screening could catch fibrosis years before symptoms appear. Lifestyle interventions (weight loss, exercise, reducing fructose) can reverse early-stage fibrosis.

Related biomarkers

These biomarkers are used in or related to the FIB-4 calculation.

AST
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ALT
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Albumin
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GGT
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Platelets
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Frequently asked questions

What is a normal FIB-4 score?
For adults under 65: below 1.30 is low risk for advanced fibrosis (F3-F4), 1.30-2.67 is indeterminate, above 2.67 is high risk. For adults 65 and older: the low-risk cutoff is raised to 2.0 because age-related changes in liver enzymes and platelet counts cause excessive false positives at the standard 1.30 threshold.
Can FIB-4 replace a liver biopsy?
FIB-4 is a screening tool, not a replacement for liver biopsy. However, its high negative predictive value means a low FIB-4 can confidently rule out advanced fibrosis without invasive testing. Indeterminate or high scores should be followed up with FibroScan or MR elastography.
Why are FIB-4 cutoffs different for patients over 65?
The standard FIB-4 cutoff of 1.30 produces unacceptably high false-positive rates in patients 65 and older, because age itself is a multiplier in the formula and platelet counts naturally decline with age. Hepatology guidelines now recommend using 2.0 as the low-risk cutoff for this age group, reducing unnecessary referrals for further testing while maintaining sensitivity for detecting true advanced fibrosis.
Why should I care about liver fibrosis?
MASLD (formerly NAFLD) affects approximately 25% of adults globally and is the leading cause of chronic liver disease. Early fibrosis is reversible with lifestyle changes, but advanced fibrosis can progress to cirrhosis and liver cancer. FIB-4 catches fibrosis early using routine blood tests.

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Sources: FIB-4 formula based on published peer-reviewed research. Reference thresholds from clinical guidelines.

  • FIB-4: An inexpensive and accurate marker of fibrosis — Hepatology

Last reviewed: April 2026. This calculator provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment.

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