AST/ALT Ratio Calculator

Two patients present with elevated liver enzymes. Their total AST and ALT values look similar on paper, but the ratio between them tells different stories. The calculator for AST/ALT ratio computes this clinically important quotient and provides the pattern interpretation that guides differential diagnosis of liver disease — alcoholic versus non-alcoholic, and the subset of elevation patterns that point toward specific diagnoses.

The AST/ALT Ratio Formula and Normal Values

The calculation is simple:

AST/ALT Ratio = Serum AST (U/L) / Serum ALT (U/L)

Normal serum enzyme levels (vary by laboratory reference range):

• AST (aspartate aminotransferase): 10–40 U/L (men); 10–35 U/L (women)
• ALT (alanine aminotransferase): 7–56 U/L (men); 7–45 U/L (women)

In healthy individuals and most non-alcoholic liver disease, the AST/ALT ratio is typically 0.8–1.0. The ratio deviates significantly in specific patterns that are diagnostically meaningful. Use this online calculator with measured enzyme values. The APRI score calculator combines AST with platelet count for hepatic fibrosis estimation.

The De Ritis Ratio: Diagnostic Patterns

The AST/ALT ratio (also called the De Ritis ratio after Italian physician Fernando De Ritis who first described it) has characteristic patterns in different liver diseases:

• Ratio above 2.0: strongly suggests alcoholic liver disease. In alcoholic hepatitis, mitochondrial AST release is disproportionate because alcohol damages mitochondria preferentially; additionally, alcohol depletes hepatic pyridoxal phosphate (B6) required for ALT synthesis, selectively reducing ALT. A ratio ≥2 has sensitivity ~70% and specificity ~80% for alcoholic liver disease among patients with hepatic steatosis.
• Ratio 1.0–2.0: intermediate — seen in cirrhosis (any cause), cardiac or skeletal muscle injury raising AST without liver disease, and some non-alcoholic cases
• Ratio below 1.0: suggests non-alcoholic fatty liver disease (NAFLD), viral hepatitis, or other non-alcoholic hepatic injury where ALT elevation typically exceeds AST

Beyond Alcohol: Other Causes of Elevated AST/ALT Ratio

The ratio interpretation requires clinical context — elevated AST/ALT ratio does not always mean alcohol:

• Cardiac injury (MI, myocarditis): AST is abundant in cardiac myocytes; a heart attack raises AST significantly without raising hepatic ALT proportionally — ratio may exceed 2–3
• Skeletal muscle injury (rhabdomyolysis): AST is present in muscle; severe exercise, trauma, or statin myopathy can elevate AST dramatically
• Cirrhosis (any cause): advanced cirrhosis may shift the ratio above 1 even without alcohol, as hepatic parenchymal loss reduces the ALT-producing hepatocyte mass
• Wilson's disease: ratio above 4 in acute Wilson's disease with hemolysis and acute liver failure

The FIB-4 index calculator and liver disease calculators provide complementary hepatic function assessment tools.

GGT and the Complete Alcoholic Pattern

The AST/ALT ratio is most specific for alcoholic liver disease when combined with an elevated GGT (gamma-glutamyl transferase). GGT is a particularly sensitive marker for alcohol use — it is elevated in over 70% of heavy drinkers. The classic alcoholic pattern is: AST/ALT ratio ≥2 + elevated GGT + normal or mildly elevated total bilirubin. When this triad is present, the probability of alcoholic liver disease is high. GGT elevation without AST/ALT ratio elevation may indicate alcohol use without significant liver injury or medications (phenytoin, barbiturates) that induce hepatic microsomal enzymes.