AST/ALT Ratio Calculator (De Ritis Ratio)

What is the AST/ALT ratio (De Ritis ratio)?

The AST/ALT ratio is AST divided by ALT; De Ritis ratio is its historical synonym. AST is found in liver, skeletal muscle, heart, and other tissues, while ALT is relatively more liver-specific. The quotient is a biochemical relationship that can provide a pattern clue, not a direct measurement of liver function, body composition, or disease cause. [1, 2, 7]

How to calculate the AST/ALT ratio

Divide same-panel AST activity by ALT activity: AST ÷ ALT. For example, AST 40 U/L and ALT 20 U/L give 40 ÷ 20 = 2.00. The same reporting unit cancels, so the result is unitless. ALT must be greater than zero because it is the denominator; AST may be zero, producing a valid quotient of 0.00. [1, 2, 9]

Why the absolute AST and ALT values still matter

AST 40 U/L with ALT 20 U/L and AST 400 U/L with ALT 200 U/L both produce 2.00. The equal ratios do not imply equal biochemical magnitude, laboratory abnormality, clinical context, or cause. Review the submitted absolute values, their trends, and the reporting laboratory's intervals rather than interpreting the quotient alone. [3, 7, 10]

What does an AST/ALT ratio above 2 mean?

AASLD's 2025 educational review describes AST/ALT >2 as a common diagnostic clue or pattern in alcohol-associated liver disease, while AST greater than ALT can also occur in cirrhosis from other causes. A ratio above 2 therefore does not establish alcohol exposure or diagnose alcohol-associated liver disease. [2, 5, 7]

Separately, the ACG 2024 criteria for probable alcohol-associated hepatitis include AST/ALT >1.5 as only one component, together with heavy alcohol use >50 g/day for a minimum of 6 months, onset of jaundice within 60 days, bilirubin >3 mg/dL, AST 50–400 U/L, and no other cause of acute hepatitis. This calculator does not collect or evaluate those criteria. [11]

What do AST/ALT ratios above 1 or below 1 mean?

A ratio above 1 means AST is numerically greater than ALT; a ratio below 1 means ALT is numerically greater than AST. Either relationship can occur in multiple hepatic and extrahepatic contexts and is not a disease-specific category. AASLD's 2025 review treats the ratio as one clue to interpret with absolute enzyme activities, other liver chemistries, history, symptoms, examination, and the broader clinical context. [1, 2, 3, 7]

Is there a normal AST/ALT ratio?

There is no single context-free AST/ALT ratio range that this calculator can safely apply as a universal “normal” classification. Laboratory AST and ALT intervals and methods vary; absolute values, extrahepatic AST sources, timing, body and disease context, and a low positive ALT denominator can all change what a quotient represents. This page therefore reports the number without assigning a category. [3, 9, 10]

What if both AST and ALT are within the laboratory reference interval?

A ratio calculated from two values within their method-specific laboratory intervals does not, by itself, establish liver disease. Use the intervals on the actual report, review trends, and interpret the absolute enzyme activities with the broader liver panel and clinical context. This calculator does not collect AST or ALT upper reference limits and cannot determine whether either submitted value is normal. [3, 4, 10]

What can change the AST/ALT ratio besides liver disease?

Skeletal-muscle injury, strenuous exercise, hemolysis or other specimen issues, cardiac injury, illness timing, medicines or supplements in the relevant context, and differences in laboratory method—including pyridoxal-phosphate use—can change one or both enzyme activities. AST is not liver-specific, so the quotient cannot identify its tissue source. [7, 8, 9]

Clinical and laboratory boundaries

ACG guidance starts evaluation with the actual enzyme abnormalities, pattern, history, and other liver chemistries. AASLD steatotic-liver-disease guidance also notes that aminotransferases can be normal in advanced disease and should not be used alone to exclude advanced fibrosis. The AST/ALT quotient is not FIB-4, APRI, elastography, biopsy, liver synthetic function, or a fibrosis stage, and it does not select tests or treatment. [3, 4, 6]

Use AST and ALT from the same specimen or contemporaneous panel in compatible units. Do not combine dates, panels, or methods. Pediatric, pregnancy, transplant, acute liver failure, and known muscle-disease assessments require their applicable clinical and laboratory pathways.