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Silent Liver (NAFLD) Fibrosis Score

Screen for Non-Alcoholic Fatty Liver Disease (NAFLD) and estimate liver scarring (fibrosis) risk. This FIB-4 score calculator uses age, AST, ALT, and platelet counts to provide a non-invasive "Liver Health Grade" and fibrosis risk level without needing an ultrasound.

Enter Values

Age

1 year120 years

AST (Aspartate Aminotransferase)

Standard range: 10-40 U/L

ALT (Alanine Aminotransferase)

Standard range: 7-56 U/L

Platelet Count

Standard range: 150-450 x 10⁹/L

Result

Enter values above and click Calculate to see your result.

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Formula

Core Formula

\text{FIB-4} = \frac{\text{Age} \times \text{AST}}{\text{Platelet Count} \times \sqrt{\text{ALT}}}

How it works: The FIB-4 index is a validated scoring system that uses basic blood markers to predict the likelihood of advanced liver fibrosis.

Review and Methodology

Updated Apr 9, 2026

This calculator runs locally in your browser. Inputs are converted into the units required by the formula, and the result is paired with supporting references so you can verify the method before using it for planning or estimates.

Worked Example

Patient Scenario: 52 years old, AST 40 U/L, ALT 30 U/L, Platelets 200 x 10⁹/L

1Step 1: Multiply Age by AST → 52 x 40 = 2,080

2Step 2: Calculate square root of ALT → sqrt(30) ≈ 5.48

3Step 3: Multiply Platelets by sqrt(ALT) → 200 x 5.48 = 1,096

4Step 4: Divide results → 2,080 / 1,096 ≈ 1.90

Result: FIB-4 Score is 1.90 (Indeterminate Risk / Grade B)

Understanding the FIB-4 Liver Health Score

The FIB-4 (Fibrosis-4) index is a simple, non-invasive screening tool used to assess the risk of advanced liver scarring (fibrosis) in patients with Non-Alcoholic Fatty Liver Disease (NAFLD) or chronic hepatitis. It helps clinicians determine which patients may need more intensive diagnostic testing, such as liver stiffness measurement or biopsy.

FIB-4 < 1.30 (Age <65): High negative predictive value (90%+) for excluding advanced fibrosis.
FIB-4 < 2.00 (Age ≥65): Adjusted threshold to account for natural aging of the liver.
FIB-4 > 2.67: Indicates a high risk of advanced fibrosis and typically warrants specialist referral.
Uses routine blood tests: AST, ALT, and Platelets are common markers in a standard Comprehensive Metabolic Panel (CMP).
Grade A (Low Risk), Grade B (Indeterminate), and Grade C (High Risk) provide a clear "Liver Health Grade" for screening purposes.

The FIB-4 score is a screening tool, not a definitive diagnosis. Always discuss results with a hepatologist or healthcare provider for full clinical context.

You can also calculate changes using our Kidney Health and CKD Risk Calculator.

FIB-4 Risk Thresholds and Interpretation

Standard clinical thresholds used for risk stratification in NAFLD patients.

FIB-4 Score	Age < 65	Age ≥ 65	Risk Level	Health Grade
< 1.30	Low Risk	Low Risk	Rule-out Fibrosis	Grade A
1.30 – 2.00	Indeterminate	Low Risk	Monitoring Needed	Grade B
2.00 – 2.67	Indeterminate	Indeterminate	Further Testing	Grade B
> 2.67	High Risk	High Risk	Specialist Referral	Grade C

Note: FIB-4 thresholds are optimized for ruling out advanced fibrosis (F3-F4 stage).

Frequently Asked Questions

What is a normal FIB-4 score?

For most adults under 65, a score below 1.30 is considered low risk and suggestive of minimal liver scarring. For those over 65, the low-risk threshold is adjusted to 2.00.

What does the FIB-4 score test for?

It screens for liver fibrosis (the accumulation of scar tissue) often caused by Non-Alcoholic Fatty Liver Disease (NAFLD), metabolic dysfunction, or chronic hepatitis.

How accurate is the FIB-4 score?

It is highly accurate at "ruling out" advanced fibrosis in low-risk patients, with a negative predictive value of over 90%. It is less definitive for "ruling in" disease, often requiring follow-up tests like a FibroScan.

What do I do if my FIB-4 score is high?

A score above 2.67 (Grade C) indicates a high risk of advanced fibrosis. You should consult a gastroenterologist or hepatologist for a definitive assessment of your liver health.

Why does age affect the FIB-4 result?

As people age, liver enzymes and blood counts can naturally fluctuate. The FIB-4 formula includes age to adjust for these changes, which is why thresholds differ for those over 65.

Can I calculate FIB-4 from a standard blood test?

Yes, if your blood work includes AST, ALT, and a Complete Blood Count (CBC) with Platelets, you have all the data needed for the calculation.

Can I use this Silent Liver (NAFLD) Fibrosis Score on my own web page?

You can. Look for the "Embed" button near the top of this calculator. It lets you pick a size, border style, and color palette, then gives you an iframe tag to paste into any webpage. The widget is responsive, loads fast, and costs nothing. More details at calculory.com/services/embed-calculators.

Medical Disclaimer

This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.

AI Assistant

Ask about this calculator

I can help you understand the silent liver (nafld) fibrosis score formula, interpret your results, and answer follow-up questions.

Try asking

Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.

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