De Ritis Ratio (AST/ALT) Calculator

Divide measured AST activity by measured ALT activity from the same laboratory panel when both are reported in the same unit. This page uses U/L and preserves the unrounded quotient before display formatting.

Sources: [1, 2]

AST and ALT can change at different rates over time. Combining results from different collection times can create a quotient that never represented one biochemical time point.

Sources: [3, 4, 7]

AST is aspartate aminotransferase and ALT is alanine aminotransferase. They are enzyme-activity measurements associated with cell injury, not direct measurements of liver function. AST also occurs in skeletal muscle, heart, and other tissues.

Sources: [1, 2, 7]

No. The ratio is unitless when AST and ALT use the same activity unit because that unit cancels during division.

Sources: [2, 9]

A submitted AST of zero produces a true arithmetic ratio of zero when ALT is positive. The source report and laboratory context still require review.

Sources: [2, 9]

ALT is the denominator. Division by zero is undefined, so this calculator cannot produce a result when ALT is zero or missing.

Sources: [2]

No universal healthy or clinical reference interval applies across laboratories, populations, methods, ages, and clinical settings. Review the absolute AST and ALT against the reporting laboratory’s own intervals.

Sources: [3, 9, 10]

No. AST/ALT >2 is a commonly discussed clue in alcohol-associated liver disease, not the current standalone alcohol-associated hepatitis threshold. Current ACG probable alcohol-associated hepatitis criteria use AST/ALT >1.5 as one component alongside heavy alcohol use >50 g/day for at least 6 months, jaundice onset within 60 days, bilirubin >3 mg/dL, AST 50–400 U/L, and no other cause of acute hepatitis. Neither ratio alone establishes alcohol exposure or a diagnosis.

Sources: [2, 5, 11]

No. The original 1957 report described a pattern in acute viral hepatitis before modern serology and molecular testing. A low ratio neither confirms nor excludes viral hepatitis today.

Sources: [1, 3, 4]

No. AST greater than ALT can accompany advanced fibrosis or cirrhosis in some populations, but the quotient cannot stage fibrosis or diagnose cirrhosis by itself.

Sources: [2, 6, 7]

Yes. Because ALT is the denominator, a low positive ALT can make the quotient large even when AST is not markedly elevated. Absolute values and their reference intervals are essential.

Sources: [2, 3]

Yes. Strenuous exercise and skeletal-muscle injury can raise AST and sometimes ALT. Creatine kinase, symptoms, timing, and the broader clinical assessment may help identify a nonhepatic contribution.

Sources: [7, 8]

Yes. In-vitro hemolysis can affect AST, and assay temperature, calibration, and pyridoxal-phosphate supplementation can influence enzyme activity. Use values from one laboratory panel and its report.

Sources: [7, 9, 10]

The division is mathematical, but reference intervals and interpretation are age-, pregnancy-, method-, and context-specific. Pediatric and pregnancy evaluation requires the applicable clinical pathway.

Sources: [3, 4, 5, 6]

No. It does not order repeat testing, imaging, viral studies, fibrosis assessment, biopsy, referral, medication, dose, admission, or treatment.

Sources: [3, 5, 7]

No. The De Ritis ratio is AST divided by ALT. The liver-injury R-value instead compares ALT and alkaline phosphatase after each is normalized to its own upper reference limit.

Sources: [3, 7]