FIB-4 Score Calculator
Use this tool to estimate liver fibrosis risk using age, AST, ALT, and platelet count.
What is the FIB-4 score?
The FIB-4 (Fibrosis-4) score is a non-invasive screening tool that estimates the likelihood of significant liver fibrosis. It combines routine lab values and age, making it practical in primary care, hepatology, and metabolic clinics.
FIB-4 is commonly used in patients with chronic liver risk factors such as:
- Metabolic dysfunction-associated steatotic liver disease (MASLD, formerly NAFLD)
- Metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH)
- Chronic hepatitis B or C
- Alcohol-related liver disease
How to use this calculator
- Enter your age in years.
- Enter your AST and ALT values in U/L from your blood test report.
- Enter platelet count as 109/L (or the same number if listed as 103/µL).
- Click Calculate FIB-4 to see your score and risk category.
How to interpret FIB-4 results
Adults age 65 and younger (common thresholds)
- Below 1.3: Low probability of advanced fibrosis
- 1.3 to 2.67: Indeterminate; consider second-line testing
- Above 2.67: Higher probability of advanced fibrosis
Adults older than 65 years (age-adjusted low threshold)
- Below 2.0: Lower risk in older adults
- 2.0 to 2.67: Indeterminate
- Above 2.67: Higher risk; further evaluation recommended
What happens after an indeterminate or high score?
FIB-4 is a triage tool, not a final diagnosis. If your score is indeterminate or high, clinicians often recommend additional evaluation such as transient elastography (FibroScan), enhanced liver fibrosis blood testing, or specialist referral.
Follow-up decisions should include your full clinical context: symptoms, medication history, alcohol use, viral hepatitis status, diabetes, BMI, and other metabolic markers.
Limitations you should know
- Not intended as a stand-alone diagnostic test.
- Can be affected by temporary changes in AST/ALT from acute illness or injury.
- Less reliable in some populations, including very young patients.
- Laboratory variability can slightly change the score.
Frequently asked questions
Is a low FIB-4 score always normal?
A low score generally suggests low probability of advanced fibrosis, but it does not exclude every liver condition. Ongoing monitoring may still be needed based on risk factors.
Can I calculate FIB-4 from old labs?
Yes, as long as the labs were measured at the same time point and units are correct. If values are outdated, repeat testing may better reflect your current liver health.
What is the biggest input mistake?
The most common error is platelet unit confusion. If your report shows platelets as 103/µL, you can enter that number directly in this calculator.
Bottom line
The FIB-4 score is a fast, evidence-based way to screen for advanced liver fibrosis risk using basic labs. Use it as a starting point, then confirm your result and management plan with your healthcare professional.