π« Hepatic Steatosis Index Calculator
A fatty-liver screen from routine labs.
For informational purposes only, not medical advice. Consult a healthcare professional.
The Hepatic Steatosis Index screens for fatty liver from routine numbers: ALT 35, AST 28, BMI 29 in a man without diabetes gives HSI = 8 Γ 1.25 + 29 = 39.0, above the 36 rule-in cutoff. Enter your labs for your score and band.
How to Use This Calculator
Lee et al. derived HSI in 2010 from ~10,000 Korean adults with ultrasound-confirmed steatosis; it validates reasonably in Western populations. It screens; imaging confirms.
Enter ALT and AST from a liver panel (U/L). The ratio matters more than either alone.
Enter BMI, sex (+2 if female), and diabetes status (+2 if diabetic).
Read the band: under 30 rules out, over 36 rules in, 30-36 is the gray zone for imaging.
The Formula
The formula's logic is transparent: the ALT/AST ratio captures hepatocellular injury pattern (ALT-dominant in steatosis), BMI captures the adiposity driving it, and the sex/diabetes points capture the two strongest demographic risk modifiers. The Γ8 weight on the ratio balances its typical range (~1.0-2.0) against BMI's (~20-40). Dual cutoffs are the honest design: rather than one threshold with mediocre accuracy, HSI gives a rule-out and a rule-in line, accepting an indeterminate middle where ultrasound decides. That middle is not a failure; it is the score telling the truth about its limits.
Worked Example
Man, ALT 35, AST 28, BMI 29, no diabetes: 8 Γ 1.25 + 29 = 39.0: rules in, discuss with clinician. Woman, ALT 22, AST 24, BMI 24, no diabetes: 8 Γ 0.92 + 24 + 2 = 33.3: indeterminate, imaging if other risks. Man, ALT 18, AST 22, BMI 23: 8 Γ 0.82 + 23 = 29.5: just under 30, rules out. I verified the tool's arithmetic. Note how BMI dominates: dropping BMI from 29 to 25 cuts 4 HSI points, which is why weight loss is the first-line therapy and the score visibly rewards it.
Why Fatty Liver Matters
| Stage | What it means |
|---|---|
| Simple steatosis (NAFL) | Fat without inflammation; often stable for years |
| NASH/MASH | Fat plus inflammation; can progress |
| Fibrosis (F2-F4) | Scarring; the stage that predicts liver outcomes |
| Cirrhosis | End-stage scarring; cancer and failure risk |
The renamed condition (MASLD/MASH) affects roughly a third of adults, most undiagnosed. Fibrosis stage, not fat amount, predicts liver-related death, which is why a rule-in HSI should lead to fibrosis assessment (FIB-4, then elastography) rather than acknowledgment alone. Cardiovascular disease, not liver failure, kills most MASLD patients: the liver finding is a metabolic warning for the whole body. For the workup chain, our FIB-4 calculator stages fibrosis risk from the same labs, our HOMA-IR calculator measures the insulin resistance underneath, and our BMI calculator tracks the driver.
Reversing It
Steatosis reverses: 7-10% weight loss resolves NASH in most patients and can regress early fibrosis. Mediterranean diet, coffee (2-3 cups associated with less fibrosis), exercise independent of weight loss, diabetes control, and alcohol abstinence (especially with steatosis) are the evidence-based moves. No drug is approved specifically for MASH as of routine practice (resmetirom's 2024 approval began changing this for F2-F3), so lifestyle remains the therapy. Recheck HSI after sustained weight loss: watching the number fall is motivating and clinically meaningful.
Limits
HSI was derived in Korean adults; performance varies by ethnicity and it has not replaced imaging anywhere. Acute liver injury (viral hepatitis, drug injury) distorts the ratio. It detects steatosis, not fibrosis: a high HSI needs FIB-4/elastography next, not alarm. And BMI misleads at muscular extremes, though less so here than in pure BMI interpretation since the liver enzymes anchor the score.
Whatever score starts the conversation, the follow-through is the same: confirm with imaging when indicated, stage fibrosis, and treat the metabolic drivers. The score is the invitation, not the diagnosis. Bring this page's number to your visit: it gives the clinician a starting point and you a shared vocabulary. That shared starting point is what turns a screening number into a plan.
HSI vs Other Fatty Liver Scores
HSI is one of several steatosis scores, each with tradeoffs. The Fatty Liver Index (FLI) adds triglycerides, GGT, and waist circumference: more accurate but needs more labs. The NAFLD Liver Fat Score adds fasting insulin and metabolic syndrome features. HSI's advantage is simplicity: ALT, AST, BMI, and two yes/no questions, all available on any basic panel. For fibrosis (the more important question), FIB-4 leads: age, AST, ALT, platelets, with validated rule-out/rule-in cutoffs. The practical cascade: HSI (or FLI) screens for fat, FIB-4 stages fibrosis risk, elastography (FibroScan) measures stiffness when FIB-4 is indeterminate or high, biopsy only when still unclear. Each step costs more and narrows the population: most people never need past FIB-4. Ask your clinician which step you are on rather than jumping to imaging from a single score.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the Hepatic Steatosis Index?
A validated fatty-liver screening score: 8Γ(ALT/AST) + BMI (+2 female, +2 diabetes). Under 30 rules out NAFLD; over 36 rules it in (Lee et al. 2010).
What HSI indicates fatty liver?
Above 36 rules in with ~92% specificity. 30-36 is indeterminate (get imaging); under 30 rules out with ~93% sensitivity.
Can fatty liver be reversed?
Yes: 7-10% weight loss resolves steatohepatitis in most patients and can regress early fibrosis. Mediterranean diet, exercise, coffee, and alcohol abstinence all help.
What is the difference between NAFLD and MASLD?
MASLD (metabolic dysfunction-associated steatotic liver disease) is the 2023 rename of NAFLD, emphasizing the metabolic roots. Same condition, updated terminology.
Does HSI detect liver fibrosis?
No: it detects steatosis (fat). Fibrosis staging needs FIB-4, elastography, or biopsy. A high HSI should prompt fibrosis assessment, not stop at the fat finding.
Why does ALT/AST ratio matter?
ALT-dominant elevation (ratio >1) typifies steatosis and viral hepatitis; AST-dominant suggests alcohol or advanced fibrosis. The pattern directs the workup.
Can you have fatty liver with normal ALT?
Yes, commonly: many MASLD patients have normal enzymes. HSI catches some via BMI, but imaging remains the sensitive test when suspicion is high.
Is fatty liver dangerous?
Simple steatosis is often stable, but progressive MASH leads to fibrosis, cirrhosis, and liver cancer. Cardiovascular disease is actually the top killer in MASLD patients.
Does alcohol affect HSI?
Alcohol causes steatosis too and raises the same enzymes; HSI does not distinguish alcoholic from metabolic fatty liver. Honest alcohol history completes the picture.
How often should HSI be rechecked?
After sustained lifestyle change (6-12 months) to track improvement, or per your clinician. It moves with weight and enzymes, making it a decent progress monitor.