FIB-4 Index optimal range and reference range

Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026

Sera's bands for FIB-4 Index:

Optimal 0 – 1.3 index; sufficient 1.3 – 2.67 index; out of range below 0 or above 2.67 index.

Evidence grade: Established clinical threshold. A band edge that corresponds to a recognised diagnostic, risk or treatment threshold from a major clinical guideline or public-health body.

All units

Unit	Optimal	Sufficient	Out of range
index	0 – 1.3	1.3 – 2.67	below 0 or above 2.67

What the evidence says

The first-line fibrosis screen in fatty liver disease, and the band edges are the published decision thresholds rather than a distribution: below 1.3 the AASLD and EASL-EASD-EASO guidelines treat advanced fibrosis as unlikely, 1.3 to 2.67 is the intermediate range that calls for a second test such as elastography, and above 2.67 the AASLD guidance advises considering specialist referral. Both guidelines use a lower cut-off of 2.0 instead of 1.3 in people over 65, and AASLD says accuracy is low under 35; Sera's band does not adjust for age. It should not be used in acute illness. Requires a date of birth on the client — without one it is not computed at all.

Sources

AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease — Rinella ME, Neuschwander-Tetri BA, Siddiqui MS, et al. — Hepatology, 2023 · Clinical guidelineFIB-4 below 1.3 is low risk and can be followed in primary care; 1.3 or above needs a second test; above 2.67 consider hepatology referral. Over 65 the cut-off is 2.0; accuracy is low under 35. Matches both Sera edges.
EASL-EASD-EASO Clinical Practice Guidelines on the Management of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) — European Association for the Study of the Liver, European Association for the Study of Diabetes, European Association for the Study of Obesity — Obesity Facts, 2024 · Clinical guidelineFIB-4 below 1.3 means low risk of advanced fibrosis, with re-assessment every 1 to 3 years; 1.3 to 2.67 is the intermediate range; over 65 the lower cut-off is 2.0. Matches both Sera edges.

What FIB-4 Index measures

A non-invasive estimate of liver fibrosis risk built from age, the two transaminases and the platelet count.

Calculated: (Age × AST) / (Platelets (×10⁹/L) × √ALT)

Related liver & pancreas health markers

See FIB-4 Index in the full list of biomarker ranges

This page is a reference for practitioners, not medical advice. Sera's bands are practitioner targets for structured review, not diagnostic thresholds, and Sera does not diagnose or recommend treatment. Read a result alongside the interval printed by the issuing laboratory and the client's history and symptoms. Range set: Sera Production, version 1.0, last reviewed November 9, 2026.