Liver risk check
FIB-4 calculator for fatty liver
FIB-4 uses your age and three common blood test values to estimate whether advanced liver scarring (fibrosis) is likely. It is the first test many liver guidelines recommend for people with fatty liver disease.
Your lab values
AST and ALT come from a liver panel or comprehensive metabolic panel; platelets from a complete blood count. Nothing you enter leaves this page.
What you will see
Your FIB-4 value, whether it falls in the low, in-between or high zone, and the usual next step for that zone.
Educational only, not medical advice. FIB-4 cannot diagnose liver disease.
Source
Formula: Sterling RK et al., Hepatology 2006. Cutoffs 1.30 and 2.67: Shah AG et al., Clin Gastroenterol Hepatol 2009. Age cutoff 2.0 at 65+: McPherson S et al., 2017.
Validated in
Created in 832 adults with HIV and hepatitis C. The 1.30 and 2.67 cutoffs were tested in 541 US adults with fatty liver disease (NASH Clinical Research Network).
Limits
Unreliable at 35 or younger; reads high in many people 65 and older. Not for acute hepatitis, heavy recent drinking or other active liver injury. It does not measure fat in the liver.
The formula
FIB-4 = (age × AST) ÷ (platelet count × √ALT), with platelets in 10⁹/L (Sterling 2006). Older age, higher AST and lower platelets all push the number up, because they track with scarring in the liver.
The cutoffs: 1.30, 2.67 and 3.25
| FIB-4 | What it suggests | Source |
|---|---|---|
| Under 1.30 | Advanced scarring unlikely | Shah 2009 (Shah 2009) |
| 1.30 to 2.67 | In between: needs a second test | Shah 2009; AASLD 2023 (AASLD 2023) |
| Over 2.67 | Advanced scarring more likely | Shah 2009 (Shah 2009) |
| Over 3.25 | The original high cutoff, from people with HIV and hepatitis C | Sterling 2006 (Sterling 2006) |
The American Association for the Study of Liver Diseases recommends FIB-4 as the first step to check for advanced scarring in people with fatty liver disease, followed by a second test such as elastography when the result is 1.30 or higher (AASLD 2023).
Why age matters
A European study of 634 people with fatty liver disease found FIB-4 worked poorly in people aged 35 or younger, and that in people 65 or older its specificity fell to 35%, meaning many false alarms (McPherson 2017). The authors proposed a low cutoff of 2.0 for people 65 and older, which raised specificity to 70% (McPherson 2017). Our calculator applies that cutoff from age 65 and warns you at 35 or younger.
Who should think about this
Fatty liver disease is common in people with overweight, type 2 diabetes or high blood pressure, and usually has no symptoms (NIDDK). If that sounds like you and you have recent blood tests, FIB-4 is a quick way to see whether scarring is worth a closer look. More in FIB-4 explained and fatty liver disease (MASLD), explained. To compare your AST with your ALT, use the AST/ALT ratio calculator. To see whether you should be tested for hepatitis C, another cause of liver scarring, use the hepatitis C screening check.
Sources
- Sterling RK, Lissen E, Clumeck N, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology. 2006;43(6):1317-1325. doi.org/10.1002/hep.21178
- Shah AG, Lydecker A, Murray K, et al. Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol. 2009;7(10):1104-1112. doi.org/10.1016/j.cgh.2009.05.033
- McPherson S, Hardy T, Dufour JF, et al. Age as a Confounding Factor for the Accurate Non-Invasive Diagnosis of Advanced NAFLD Fibrosis. Am J Gastroenterol. 2017;112(5):740-751. doi.org/10.1038/ajg.2016.453
- Rinella ME, Neuschwander-Tetri BA, Siddiqui MS, et al. AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease. Hepatology. 2023;77(5):1797-1835. doi.org/10.1097/HEP.0000000000000323
- National Institute of Diabetes and Digestive and Kidney Diseases (NIH). Nonalcoholic Fatty Liver Disease (NAFLD) and NASH. www.niddk.nih.gov/health-information/liver-disease/nafld-nash
- MedlinePlus (National Library of Medicine). Liver Function Tests. medlineplus.gov/lab-tests/liver-function-tests/
- MedlinePlus (National Library of Medicine). Complete Blood Count (CBC). medlineplus.gov/lab-tests/complete-blood-count-cbc/
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-10-29. Spotted an error? See About.