What is a normal FIB-4 score?

There is no normal range, only cut-offs. Below 1.3 means advanced liver scarring is unlikely. 1.3 to 2.66 is indeterminate, and 2.67 or above means advanced scarring is likely. From age 65 the lower cut-off is 2.0, because FIB-4 rises with age alone.

How is FIB-4 calculated?

Age × AST, divided by platelets (×10⁹/L) × the square root of ALT. For example, age 52, AST 40, ALT 36 and platelets 210 give (52 × 40) ÷ (210 × 6) = 1.65.

What should I do if my FIB-4 is between 1.3 and 2.67?

Guidelines from liver societies recommend a second test, usually a FibroScan (vibration-controlled elastography) or an ELF blood test. Most people in this range turn out not to have advanced scarring, but only the second test can tell.

Why do some sites use 1.45 and 3.25?

Those were the original cut-offs from the 2006 paper that introduced FIB-4, in people with HIV and hepatitis C. For fatty liver, the 1.3 and 2.67 cut-offs (Shah, 2009) are the ones liver guidelines use today, including the American liver society’s 2023 guidance.

Is FIB-4 accurate under 35?

It was developed and checked in adults, and it is less reliable under 35. Because age is in the formula, it also reads higher in older people, which is why the cut-off moves to 2.0 from 65.

FIB-4 calculator for liver fibrosis

Short answer: FIB-4 estimates liver scarring (fibrosis) from four routine numbers: age, AST, ALT and platelets. Below 1.3, advanced fibrosis is unlikely; 2.67 or above, it is likely; in between, a second test such as a FibroScan decides. From age 65 the lower cut-off is 2.0.

Free calculator

FIB-4 calculator (liver fibrosis)

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

Sources: Sterling RK, Lissen E, Clumeck N, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology 2006;43(6):1317-1325.

Age

years

AST (also called SGOT)

U/L

In U/L

ALT (also called SGPT)

U/L

In U/L

Platelets

×10⁹/L

×10⁹/L is the same number as ×10³/µL or K/µL

Your result

Enter the numbers from your lab report to see your result.

FIB-4 was built for people with a liver condition such as fatty liver or hepatitis. It is a first check that decides whether a scan such as a FibroScan is needed, not a diagnosis.

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A pointer, not a diagnosis. Talk to a doctor about your result, and sooner if you feel unwell.

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How to read the result

Low (below 1.3)< 1.3Advanced liver scarring is unlikely. If you have a liver condition, doctors usually repeat FIB-4 every one to three years.
In between (1.3 to 2.66)1.3 – 2.67Not clear either way. Guidelines suggest a second test, usually a FibroScan (a painless ultrasound-like scan) or an ELF blood test, to settle it. Talk to a doctor about arranging one.
High (2.67 or above)≥ 2.67Advanced liver scarring is more likely. This needs a doctor, who will usually arrange a FibroScan or a referral to a liver specialist. Scarring found early can often be stopped or partly reversed.

Your lab’s range

FIB-4 is not printed on most lab reports, and it has no normal range: it is read against the cut-offs above. The four numbers it uses do have lab ranges (AST and ALT up to about 40 U/L, platelets about 150–400 ×10⁹/L), and FIB-4 can be raised even when each of them is in range.

How it is worked out

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

FIB-4 was built for people with a liver condition such as fatty liver or hepatitis. It is a first check that decides whether a scan such as a FibroScan is needed, not a diagnosis.

Sources

Sterling RK, Lissen E, Clumeck N, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology 2006;43(6):1317-1325.
Shah AG, Lydecker A, Murray K, et al. Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol 2009;7(10):1104-1112.
McPherson S, Hardy T, Dufour JF, et al. Age as a confounding factor for the accurate non-invasive diagnosis of advanced NAFLD fibrosis. Am J Gastroenterol 2017;112(5):740-751.
Rinella ME, Neuschwander-Tetri BA, Siddiqui MS, et al. AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease. Hepatology 2023;77(5):1797-1835.

The markers it uses

SGOT (AST)SGPT (ALT)Platelet Count

Questions

What is a normal FIB-4 score?: There is no normal range, only cut-offs. Below 1.3 means advanced liver scarring is unlikely. 1.3 to 2.66 is indeterminate, and 2.67 or above means advanced scarring is likely. From age 65 the lower cut-off is 2.0, because FIB-4 rises with age alone.
How is FIB-4 calculated?: Age × AST, divided by platelets (×10⁹/L) × the square root of ALT. For example, age 52, AST 40, ALT 36 and platelets 210 give (52 × 40) ÷ (210 × 6) = 1.65.
What should I do if my FIB-4 is between 1.3 and 2.67?: Guidelines from liver societies recommend a second test, usually a FibroScan (vibration-controlled elastography) or an ELF blood test. Most people in this range turn out not to have advanced scarring, but only the second test can tell.
Why do some sites use 1.45 and 3.25?: Those were the original cut-offs from the 2006 paper that introduced FIB-4, in people with HIV and hepatitis C. For fatty liver, the 1.3 and 2.67 cut-offs (Shah, 2009) are the ones liver guidelines use today, including the American liver society’s 2023 guidance.
Is FIB-4 accurate under 35?: It was developed and checked in adults, and it is less reliable under 35. Because age is in the formula, it also reads higher in older people, which is why the cut-off moves to 2.0 from 65.

More calculators for the same system

APRI calculator (AST to platelet ratio)De Ritis ratio calculator (AST/ALT)Albumin/globulin (A/G) ratio calculator

All blood test calculators

A pointer, not a diagnosis. Talk to a doctor about your result, and sooner if you feel unwell. Reference ranges are general-population guidance compiled from common clinical laboratories, not a diagnosis. Lab-to-lab ranges differ. Always read your results with your doctor.