Non-Invasive Liver Assessment

FIB-4 Score Calculator

Estimate liver fibrosis risk using age, liver enzymes, and platelet count — no biopsy required.

📋 Enter Patient Values

Age years

AST U/L

ALT U/L

Platelets ×10⁹/L

⚠ Please fill in all fields with valid positive values.

FIB-4 Score

Low Risk Indeterminate High Risk

The FIB-4 Formula

FIB-4 = (Age × AST) ÷ (Platelets × √ALT)

Age in years · AST & ALT in U/L · Platelets in ×10⁹/L
Originally validated in HIV/HCV coinfection; widely adopted in NAFLD/MASLD and chronic liver disease.

📊 Score Interpretation

FIB-4 Range	Risk Category	Likely Fibrosis Stage	Suggested Action
< 1.30	Low	F0–F1 (None–Mild)	Routine monitoring; reassess in 1–2 years
1.30 – 2.67	Indeterminate	F1–F3 (Mild–Moderate)	Consider additional testing (elastography, ELF)
> 2.67	High	F3–F4 (Advanced–Cirrhosis)	Refer to hepatology; consider liver biopsy

* Age-adjusted thresholds may apply: some guidelines use <2.0 (low) and >4.0 (high) for patients aged >65 years.

Understanding Your Inputs

🩸 AST & ALT

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are liver enzymes released when liver cells are damaged. Elevated levels suggest hepatocellular injury. The AST/ALT ratio can also hint at the cause (e.g., ratio >2 suggests alcoholic liver disease).

💊 Platelet Count

Platelets decrease as liver fibrosis advances. Portal hypertension from cirrhosis causes splenic sequestration and reduced thrombopoietin production, both lowering platelet counts. A count below 150 ×10⁹/L warrants further assessment.

📅 Why Age Matters

Fibrosis progresses over time, so older age intrinsically increases the score. In older patients (>65 yrs), FIB-4 tends to overestimate fibrosis. Age-specific cut-offs improve specificity in this population.

🔬 Normal Lab Ranges

AST10–40 U/L

ALT7–56 U/L

Platelets150–400 ×10⁹/L

FIB-4 (low risk)< 1.30

ℹ️ Limitations & Clinical Context

Not a standalone diagnostic. FIB-4 stratifies risk; it does not replace liver biopsy or imaging in ambiguous cases.
Validated populations. Originally derived in HIV/HCV coinfection; subsequently validated in NAFLD/MASLD, alcoholic liver disease, and chronic viral hepatitis.
False elevations. Acute hepatitis, strenuous exercise, haemolysis, or hypothyroidism can raise AST and skew the score upward.
Complementary tools. Liver stiffness measurement (FibroScan / transient elastography), Enhanced Liver Fibrosis (ELF) panel, and APRI score may be used alongside FIB-4 for a more complete picture.
Dynamic score. Repeat testing after lifestyle changes, weight loss, or treatment can reflect improvement in fibrosis burden.

⚕ Medical Disclaimer This calculator is intended for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. FIB-4 results should always be interpreted by a qualified healthcare provider in the context of the patient's full clinical picture, history, and other investigations. Never disregard professional medical advice or delay seeking it because of information obtained from this tool. If you are concerned about your liver health, please consult your doctor or a hepatologist.