AST/ALT Ratio Calculator (De Ritis Ratio)

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

The AST/ALT ratio, also called the De Ritis ratio after the Italian physician Fernando De Ritis who described its diagnostic utility in 1957, is simply your AST (aspartate aminotransferase) level divided by your ALT (alanine aminotransferase) level. Both enzymes are measured in units per litre (U/L) on a standard liver function blood panel. While the absolute levels of AST and ALT tell you whether there is liver stress, the ratio between them gives a clue about the likely cause. The ratio works because the two enzymes behave differently depending on what is damaging the liver: alcohol-related injury tends to raise AST disproportionately, while viral and metabolic causes tend to raise ALT more. In healthy adults both enzymes sit in roughly equal concentrations in the blood, so the normal ratio is close to 1.0.

How to read your result

A ratio below 1.0 means your ALT is higher than your AST, the pattern most often seen with nonalcoholic fatty liver disease (NAFLD/NASH), acute viral hepatitis, and drug-induced liver injury. A ratio between 1.0 and 2.0 is non-specific and can appear in chronic hepatitis B or C, moderate alcohol use, some stages of cirrhosis, or even after vigorous exercise. A ratio at or above 2.0 (especially when transaminases are meaningfully elevated) is the classic pattern of alcoholic hepatitis described in the original De Ritis literature. A ratio above 3.0 makes that pattern even stronger. Very high ratios (above 5.0) can also reflect non-hepatic causes where AST rises from muscle, heart, or kidney tissue rather than liver cells. The ratio only has useful discriminating power when at least one enzyme is elevated above the normal reference range - a ratio of 2.0 with both enzymes at the low end of normal means much less than a ratio of 2.0 with both enzymes several times the upper limit of normal.

Why alcohol raises AST more than ALT

The biological reason alcoholic liver disease produces an AST-predominant pattern is well understood. ALT synthesis depends on pyridoxal-5-phosphate (the active form of vitamin B6) more than AST synthesis does, and chronic alcohol use depletes vitamin B6. This means the liver can produce less ALT relative to AST. In addition, the specific type of liver cell damage caused by alcohol (mitochondrial injury) liberates the mitochondrial isoform of AST, which is less abundant in other liver diseases, further pushing the ratio upward. This is why some laboratories separate cytoplasmic AST from total AST, though most routine panels report total AST only.

Important limitations of the ratio

The De Ritis ratio is a screening and pattern-recognition tool, not a standalone diagnostic test. Several important caveats apply. First, both AST and ALT are found in tissues beyond the liver - particularly skeletal muscle, cardiac muscle, and red blood cells. Heavy exercise, rhabdomyolysis, haemolysis, and myocardial infarction can all raise AST (and to a lesser extent ALT) without any liver disease being present. Second, the ratio loses its discriminating power when both values are only mildly elevated. Third, in late-stage acute liver failure, AST clears from the bloodstream faster than ALT, so a falling ratio can paradoxically coincide with worsening clinical condition. Reference ranges also vary slightly between laboratories and between men and women, and some guidelines apply sex-specific upper limits for ALT in particular. Always interpret the ratio alongside the absolute enzyme levels, GGT, alkaline phosphatase, bilirubin, albumin, prothrombin time, clinical history, imaging, and, where appropriate, liver biopsy.