How FIB-4 is calculated
FIB-4 combines age, AST, ALT and platelet count. Platelets are converted to ×10⁹/L before calculation; classification uses the full unrounded score.
FIB-4 = (Age × AST) ÷ (Platelets × √ALT)
WorklityLiver health screening
FIB-4 Liver Fibrosis Risk Calculator
MASLD / NAFLDUse age and routine blood-test values to estimate a FIB-4 score for liver-fibrosis risk stratification.
Enter valid values and calculate to see your result.
MASLD / NAFLD interpretation
For ages 35–64, scores below 1.30 are lower risk, 1.30 through 2.67 are intermediate, and scores above 2.67 are higher risk. From age 65, the lower threshold is adjusted to 2.00 while the upper threshold remains 2.67.
Important limitations
- FIB-4 is a non-invasive risk-stratification aid, not a diagnosis.
- It cannot diagnose or exclude liver fibrosis, cirrhosis or liver disease by itself.
- A low result cannot completely exclude significant fibrosis.
- Age, other health conditions and the clinical situation can affect interpretation.
- FIB-4 is less reliable below age 35.
- Acute illness or temporarily, markedly abnormal liver enzymes can make interpretation inappropriate.
Frequently asked questions
What is FIB-4?
FIB-4 is a calculation using age, AST, ALT and platelet count to help stratify the risk of liver fibrosis.
Does a low score rule out liver fibrosis?
No. A low score lowers estimated risk in the intended context but cannot completely exclude significant fibrosis.
Why is the threshold different from age 65?
Age affects FIB-4, so MASLD guidance uses a higher lower-risk threshold for older adults.
What should I do with an intermediate or higher result?
Discuss it with a qualified healthcare professional, who can decide whether clinical review or a secondary assessment is appropriate.
Sources / References
These references support the formula, risk-stratification approach and limitations. They do not endorse Worklity.