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 index is a non-invasive liver fibrosis score commonly used to estimate the likelihood of advanced fibrosis, especially in people with chronic liver disease or metabolic risk factors. It combines four widely available clinical values:
- Age
- AST (aspartate aminotransferase)
- ALT (alanine aminotransferase)
- Platelet count
FIB-4 formula
The formula used in this calculator is:
FIB-4 = (Age × AST) / (Platelets × √ALT)
Because these are routine lab values, FIB-4 is often used as a first-step triage tool before imaging tests such as elastography.
How to interpret your result
| Age Group | FIB-4 Range | Typical Interpretation |
|---|---|---|
| Under 65 years | < 1.30 | Lower likelihood of advanced fibrosis |
| Under 65 years | 1.30 to 2.67 | Indeterminate; may need further testing |
| Under 65 years | > 2.67 | Higher likelihood of advanced fibrosis |
| 65 years and older | < 2.00 | Lower likelihood (age-adjusted threshold) |
| 65 years and older | 2.00 to 2.67 | Indeterminate zone |
| 65 years and older | > 2.67 | Higher likelihood of advanced fibrosis |
How this calculator helps in practice
FIB-4 is useful in primary care and specialty settings because it can quickly identify who may need additional liver evaluation. In many pathways, people with low scores can often be monitored, while indeterminate or high scores trigger follow-up testing.
Common next steps after calculation
- Review trend over time, not just one value
- Confirm lab abnormalities and rule out acute causes
- Consider elastography or specialist referral for indeterminate/high results
- Address metabolic risk factors (weight, glucose, lipids, blood pressure)
- Limit alcohol and review medication safety with your clinician
Limitations you should know
No score is perfect. FIB-4 may be less reliable in acute illness, active inflammation, very young adults, and certain blood or liver conditions that affect platelets or enzymes for reasons unrelated to fibrosis. It should be interpreted alongside history, exam, imaging, and other labs.
Frequently asked questions
Is a high FIB-4 a diagnosis of cirrhosis?
No. A high value indicates increased risk and should prompt proper clinical evaluation, not self-diagnosis.
Can FIB-4 go down over time?
Yes. Improvements in liver inflammation, metabolic health, and underlying causes can lower the score in some people.
Why does age matter so much in this formula?
Age is directly included in the equation, which is why older adults can have higher scores even with similar lab values. That is one reason age-adjusted interpretation is commonly used.
Bottom line
FIB-4 is a practical, low-cost way to estimate fibrosis risk using routine labs. It works best as part of a broader clinical decision process. Use this calculator as a starting point, then discuss results with your healthcare professional for personalized guidance.