Article — AST/ALT Ratio Calculator
AST/ALT ratio calculator (De Ritis ratio)
The AST/ALT ratio, also called the De Ritis ratio, divides aspartate aminotransferase by alanine aminotransferase. A healthy adult ratio sits between 0.8 and 1.1. A ratio under 1 suggests hepatocellular injury (viral hepatitis, NAFLD); a ratio above 2 is the classic alcoholic liver disease pattern. The ratio is a screening tool, not a diagnosis.
Fernando De Ritis published the ratio in 1957 after noticing that alcoholic and viral liver injury produced opposite enzyme patterns. The math has not changed in seven decades. What has changed is our understanding of which patterns mean what, and how much weight to give the ratio when other workup is available.
What is the AST/ALT ratio
AST and ALT are aminotransferases — enzymes that move amino groups between amino acids during metabolism. Both leak into the bloodstream when hepatocytes are damaged. ALT lives mostly in liver cytosol and is reasonably liver-specific. AST is found in liver mitochondria, heart muscle, skeletal muscle, red blood cells, and kidney, so it is less specific but more sensitive to certain injury patterns.
Because the two enzymes come from different intracellular pools, the ratio between them tracks what kind of damage is happening. Cytosolic injury without mitochondrial involvement (typical of viral hepatitis) raises ALT more than AST. Mitochondrial injury (typical of alcohol toxicity) releases mitochondrial AST and tips the ratio above 1.
The De Ritis ratio is one of the oldest still-used lab calculations in modern hepatology — it predates the discovery of hepatitis B (1965) and hepatitis C (1989). It survived because it remains a useful free signal layered on top of every routine liver panel.
Interpreting the AST/ALT ratio
Clinicians read the ratio in four bands. Below 1 is the hepatocellular pattern. Between 0.8 and 1.1 with both enzymes in range is healthy. From 1 to 2 is the mixed or non-specific pattern. Above 2 — particularly with elevated GGT — is the alcoholic pattern. Above 3 with low albumin and prolonged INR raises concern for advanced cirrhosis from any cause.
- Ratio < 1 = ALT > AST, hepatocellular pattern (viral hepatitis, NAFLD/MASLD, drug-induced)
- 0.8 - 1.1 = normal range when both enzymes are in reference limits
- Ratio 1.0 - 2.0 = mixed pattern, needs context and additional labs
- Ratio > 2 = alcoholic liver disease pattern, especially with high GGT
- Ratio > 3 = advanced fibrosis or cirrhosis from any cause
- AST reference = 10-40 U/L (varies by lab)
- ALT reference = 7-56 U/L (some labs use tighter limits)
How to use the AST/ALT ratio calculator
Enter your AST and ALT values in U/L directly from your liver panel. The calculator divides them and shows the resulting ratio along with the relevant band, plus a quick read on whether each enzyme is in, above, or below reference range. The interpretation text suggests which differential diagnoses are most consistent with your numbers.
A worked example: AST 150 U/L, ALT 60 U/L. The ratio is 2.5, with both enzymes clearly elevated. The pattern is classic alcoholic liver disease and the next step is GGT, ferritin, and an alcohol history. Another example: AST 25 U/L, ALT 110 U/L. The ratio is 0.23, AST is in range, ALT is markedly elevated — a hepatocellular pattern that needs viral serologies and a metabolic workup for NAFLD.
< 1.0 hepatocellular0.8 - 1.1 healthy1.0 - 2.0 mixed pattern> 2.0 alcoholic / cirrhosisAST/ALT ratio in alcoholic liver disease
Alcoholic liver disease produces the highest AST/ALT ratios you will see in clinical practice. The mechanism is specific: ethanol injures hepatocyte mitochondria and depletes pyridoxal phosphate, the cofactor that ALT needs more than AST. So mitochondrial AST escapes while ALT synthesis falters. The result is a ratio frequently above 2, often above 3, and occasionally above 5 in florid alcoholic hepatitis.
The American Association for the Study of Liver Diseases notes that AST rarely exceeds 500 U/L in alcoholic disease — values higher than that should prompt a search for a second insult like acetaminophen toxicity. GGT elevations above 100 IU/L alongside a ratio above 2 are particularly suggestive of recent heavy drinking.
AST/ALT ratio in NAFLD and MASH
Non-alcoholic fatty liver disease — recently renamed MASLD (metabolic dysfunction-associated steatotic liver disease) — typically shows the opposite pattern. Early MASLD has a ratio below 1, with mildly elevated ALT and a near-normal AST. As disease progresses through metabolic dysfunction-associated steatohepatitis (MASH) toward cirrhosis, the ratio gradually climbs. Crossing above 1 in a known MASLD patient is a marker that advanced fibrosis may be developing.
An AST/ALT ratio greater than 1 in a non-drinker with metabolic syndrome is a flag worth following up. The Fib-4 score, which combines AST, ALT, platelets, and age, is the standard next step for non-invasive fibrosis screening.
Limitations of the De Ritis ratio
The ratio has real limits. Hemolyzed samples falsely elevate AST and push the ratio up — always repeat on a clean draw if the lab reports hemolysis. Skeletal muscle injury (rhabdomyolysis, statin myopathy, intense exercise) raises AST without any liver involvement. Acute viral hepatitis can produce sky-high ALT and an artificially low ratio that does not reflect the underlying disease severity.
An abnormal AST/ALT ratio always needs interpretation alongside history, exam, and additional labs. Do not use this calculator as a substitute for clinical care. Liver disease is most often diagnosed by a constellation of findings, not one number.
Labs to order alongside AST/ALT
For any abnormal AST/ALT pattern, the standard follow-up panel includes GGT, alkaline phosphatase, total and direct bilirubin, albumin, INR, and a CBC. The first round of etiology testing usually adds hepatitis A IgM, hepatitis B surface antigen, hepatitis C antibody, and ferritin. For young adults, alpha-1 antitrypsin and ceruloplasmin are added to rule out genetic causes. Right upper quadrant ultrasound provides anatomy and a screen for steatosis or cirrhosis.
The combined picture — enzyme pattern, synthetic function (albumin, INR), cholestatic markers (alk phos, GGT), and imaging — gives a hepatologist enough to land on a working diagnosis. The De Ritis ratio is one piece of that puzzle. A useful piece, but never the whole picture.