Estimates the risk of advanced liver fibrosis from age, AST, ALT and the platelet count.
Result
Enter the age, AST, ALT and platelet count.
Sources
AASLD 2023 · 3 studies
AASLD 2023 FIB-4 first, then liver stiffness or ELF if 1.3 or more.
3
studies
5,196
citations
5,505
PubMed papers
Evidence
Guideline recommendation
“All patients with hepatic steatosis or clinically suspected NAFLD based on the presence of obesity and metabolic risk factors should undergo primary risk assessment with FIB-4. … If FIB-4 is ≥ 1.3, VCTE, MRE, or ELF may be used to exclude advanced fibrosis.”
American Association for the Study of Liver Diseases
Hepatology: Journal Metrics Score 6.5, Q1 · cited 3,030 times
PubMed · Free full text · DOI
Known limitations
Developed in 832 patients with HIV/HCV coinfection. In the validation set, a FIB-4 below 1.45 had a negative predictive value of 90% for advanced fibrosis (Ishak 4 to 6) and above 3.25 a positive predictive value of 65%; using the two cut-offs could have avoided biopsy in 71% of the validation group.
Hepatology: Journal Metrics Score 6.5, Q1 · cited 5,196 times
In 847 liver biopsies from patients with hepatitis C, a FIB-4 below 1.45 excluded severe fibrosis (F3 to F4) with a negative predictive value of 94.7%, and above 3.25 confirmed it with a positive predictive value of 82.1%; the area under the curve was 0.85.
Hepatology: Journal Metrics Score 6.5, Q1 · cited 2,142 times
In 634 patients with biopsy-proven fatty liver disease, FIB-4 discriminated poorly at 35 or younger (area under the curve 0.60), and at 65 or older its specificity for advanced fibrosis fell to 35%. A lower cut-off of 2.0 from 65 raised specificity to 70% with a sensitivity of 77%.
Am J Gastroenterol: Journal Metrics Score 0.5, Q4 · cited 1,003 times
PubMed · Free full text · DOI
The original paper has been cited 5,196 times, and 5,505 PubMed articles mention the FIB-4 index in their title or abstract. Citation counts from OpenAlex and article counts from PubMed, retrieved November 14, 2026. Journal Metrics Scores and quartiles are from this site’s current release; follow the journal name for details.
After the result
High (2.67 or above) · Indeterminate (1.3 to below 2.67) · Low (below 1.3, or 2.0 or below from 65)
Specialist assessment. Second test. Manage risk factors and repeat.
Next steps
Avoid common errors
5 common errors to avoid
and 3 more
When FIB-4 misleads
1Age drives the index
Age is in the numerator, so an older patient with normal liver tests can score in the indeterminate range. Use 2.0 as the lower cut-off from 65.
2Young adults
At 35 or younger FIB-4 discriminated poorly, so a low value does not exclude fibrosis well.
3Low platelets from other causes
Immune thrombocytopenia, marrow disease, chemotherapy or hypersplenism of another cause lower the platelet count and raise FIB-4 without fibrosis.
4Acute hepatitis
Very high AST from acute injury, alcohol binges or muscle damage raises FIB-4; it is for chronic liver disease with stable tests.
5Not a diagnosis
FIB-4 sorts risk. It misses some advanced fibrosis and flags people without it; the indeterminate group is large.
Formula
(age × AST) ÷ (platelets × √ALT); below 1.3 low, 2.67 or above high; from 65, 2.0 or below is low.
(age × AST) ÷ (PLT × √ALT)
(age × AST) ÷ (platelets × √ALT); below 1.3 low, 2.67 or above high; from 65, 2.0 or below is low.
Formula and cut-offs
| Item | Value |
|---|---|
| FIB-4 | (age [years] × AST [U/L]) ÷ (platelets [10⁹/L] × √ALT [U/L]) |
| Fatty liver disease | below 1.30 low, 1.30 to below 2.67 indeterminate, 2.67 or above high (Shah 2009; AASLD 2023) |
| Age 65 or older | in fatty liver disease, 2.0 or below is low risk instead of below 1.3 (McPherson 2017; AASLD 2023) |
| Hepatitis C, HIV/HCV | below 1.45 advanced fibrosis unlikely, above 3.25 likely (Sterling 2006; Vallet-Pichard 2007) |
| Result | FIB-4 | Meaning |
|---|---|---|
| Low risk of advanced fibrosis | below 1.3 (2.0 or below from age 65) | Advanced fibrosis (F3 to F4) is unlikely. In fatty liver disease a FIB-4 of 1.30 or less had a negative predictive value of 90% in the study that set this cut-off. |
| Indeterminate | 1.3 to below 2.67 | FIB-4 can neither exclude nor confirm advanced fibrosis. Guidance advises a second test, such as liver stiffness by transient elastography or the ELF blood test. |
| High risk of advanced fibrosis | 2.67 or above | Advanced fibrosis is more likely. In a specialist fatty liver cohort a FIB-4 of 2.67 or more had a positive predictive value of 80%; it is lower where advanced fibrosis is less common, such as primary care. Specialist assessment is advised. |
Sterling 2006
Shah 2009
Units
Test cases
3 published cases, each also a test case
3 published cases; the calculator reproduces every index.
Worked examples
A 47-year-old woman with massive polycystic liver disease and severe malnutrition was assessed for living-donor liver transplantation. AST was 11 IU/L, ALT 7 IU/L and the platelet count 254 ×10⁹/L; Table 1 gives a FIB-4 of 0.77, and the text notes that the fibrosis markers were normal. She had a successful transplant.
“fibrosis-4 (FIB-4) index, and the platelet count were within normal ranges”
A low FIB-4 here is correct, since cysts rather than fibrosis enlarged the liver. It also shows the limit of the index: it measures fibrosis, not every serious liver disease.
Entered as: Age: 47 years; AST: 11 U/L; ALT: 7 U/L; Platelet count: 254 ×10⁹/L (×10³/µL).
Source: Takakusagi S et al., Intern Med 2022 (PubMed · Free full text · DOI)
A 62-year-old man with cardiovascular risk factors had post-prandial abdominal pain from median arcuate ligament syndrome. Routine bloods showed AST 27 U/L, ALT 18 U/L, platelets 165 ×10⁹/L and an INR of 1.30; the report gives a FIB-4 of 2.39, intermediate risk.
“the patient had a Fibrosis-4 (FIB-4) score of 2.39, which placed him in the intermediate-risk zone”
Normal transaminases can still give an indeterminate FIB-4 at this age, because age is in the numerator. By the AASLD pathway for patients at risk of fatty liver disease, the next step would be liver stiffness measurement or ELF; the authors advised longitudinal follow-up.
Entered as: Age: 62 years; AST: 27 U/L; ALT: 18 U/L; Platelet count: 165 ×10⁹/L (×10³/µL).
Source: Kubba R et al., Cureus 2026 (PubMed · Free full text · DOI)
A 50-year-old man with hepatitis B had a giant regenerative nodule in a cirrhotic liver. AST was 69.4 IU/L, ALT 107.8 IU/L and platelets 80 ×10⁹/L; the report gives a FIB-4 of 4.18, above the 3.25 cut-off for advanced fibrosis.
“FIB-4 of 4.18”
The calculator gives 4.18, as reported; it is above both 2.67 and the original 3.25 cut-off. The low platelet count, likely from portal hypertension (the portal vein was dilated), drives much of the value.
Entered as: Age: 50 years; AST: 69.4 U/L; ALT: 107.8 U/L; Platelet count: 80 ×10⁹/L (×10³/µL).
Source: Li L et al., J Clin Transl Hepatol 2022 (PubMed · Free full text · DOI)
FAQ
6 questions and answers
and 4 more answers
Questions
FIB-4 = (age × AST) ÷ (platelet count × √ALT), with age in years, AST and ALT in U/L and platelets in 10⁹/L. A 50-year-old with AST 40, ALT 36 and platelets 200 has (50 × 40) ÷ (200 × 6) = 1.67.
There is no single normal value. In fatty liver disease a FIB-4 below 1.3 makes advanced fibrosis unlikely, above 2.67 makes it likely, and values in between are indeterminate. From age 65 a lower cut-off of 2.0 is used, because age alone pushes the index up.
FIB-4 was built in people with HIV and hepatitis C, where 1.45 and 3.25 were chosen (Sterling 2006). Later work in fatty liver disease chose 1.30 and 2.67 (Shah 2009), and these are the cut-offs in AASLD 2023 guidance. The calculator reports both.
A second test: liver stiffness by vibration-controlled transient elastography (FibroScan), or the ELF blood test where that is used. Guidance for fatty liver disease uses this two-step approach to decide who needs a hepatologist.
Less so. At 35 or younger it performed poorly, so a low value is less reassuring. At 65 or older, the 1.3 cut-off flags too many people without fibrosis, so 2.0 is used as the lower cut-off.
No. It was built for chronic liver disease. Very high transaminases from acute injury raise the index without reflecting fibrosis; repeat it once the liver tests have settled.
Further reading
8 references with PubMed and DOI links
8
references
6
free full text
From Sterling RK et al., Hepatology 2006 to the newest case reports.
References
clinical grade of aneurysmal subarachnoid hemorrhage, I to V.
total calcium adjusted for albumin, in mg/dL or mmol/L.
stroke severity from 15 bedside items, 0 to 42.
MAP from systolic and diastolic pressure, against the 65 mm Hg target.
eye, verbal and motor scores for preverbal children, 3 to 15.
oxygenation ratio with the Berlin ARDS severity ranges.
serum sodium corrected for high glucose, Katz or Hillier factor.
sodium − (chloride + bicarbonate), with the albumin-corrected gap.
urea nitrogen to creatinine ratio, in US or SI units.
estimated creatinine clearance with actual, ideal or adjusted weight.
cardiac output and index from oxygen consumption and saturations.
ANC from the white cell count, neutrophils and bands.
insulin resistance from fasting glucose and insulin, in US or SI units.
FENa from plasma and urine sodium and creatinine: prerenal, indeterminate or tubular pattern.
three-item stroke severity screen for large vessel occlusion, 0 to 4.
water deficit in hypernatremia from sodium, weight and body water.
expected PaCO2 in metabolic acidosis, 1.5 × HCO3 + 8 ± 2.
corrected QT interval by Bazett, Fridericia, Framingham or Hodges.
head CT decision rule for children with minor head trauma.
blood loss before hemoglobin or hematocrit reaches a chosen lowest value.
eye, verbal and motor response, 3 to 15, with GCS-Pupils.
Devine ideal body weight and adjusted weight from height and sex.
cuffed and uncuffed tube size and oral depth by age.
calculated osmolality, osmolal gap and ethanol correction.
severity of alcohol-associated hepatitis from prothrombin time and bilirubin.
MELD, MELD-Na and MELD 3.0 for chronic liver disease.
early stroke risk after a transient ischemic attack.
whether a patient with blunt trauma needs cervical spine imaging.
prognosis from a Bruce protocol exercise test.
alveolar–arterial oxygen gradient from a blood gas.
whether an adult with minor head injury needs CT.
Which published the original FIB-4 paper, with its current metrics.
Contributed by Dr. Meng Zhao (MD · Former Neurosurgeon · Medical AI Researcher), from the original publications listed here. Last updated November 14, 2026. LinkedIn
The calculator code is tested against every worked example on this page before each release.
This calculator supports, and does not replace, clinical judgment. It is meant for healthcare professionals and is not medical advice for patients. Report an error through the contact page.