AST/ALT Ratio (De Ritis Ratio) Calculator
AST/ALT Ratio (De Ritis Ratio) Calculator
Calculate the De Ritis ratio and read what its value suggests about the cause and stage of liver injury.
AST/ALT Ratio (De Ritis Ratio)
AST ÷ ALTAST 96 U/L, ALT 42 U/L
Formula
- AST
- aspartate aminotransferase, U/L — present in liver, muscle, heart and red cells
- ALT
- alanine aminotransferase, U/L — far more liver-specific
Worked example
AST 96 U/L, ALT 42 U/L
96 ÷ 42 = 2.29
Above 2 → alcohol-related injury pattern
Patterns
| Ratio | Suggests |
|---|---|
| < 1 | Early NAFLD, chronic viral hepatitis, drug injury |
| > 1 in known NAFLD | Progression to advanced fibrosis |
| > 2 with raised GGT | Alcohol-related liver disease |
| > 2 with normal ALT | Consider a muscle source — check CK |
| > 4 | Consider Wilson disease in a young patient |
What the ratio tells you
The two transaminases differ in where they live. ALT is largely confined to hepatocyte cytosol and is the more liver-specific of the pair. AST is present in liver but also in skeletal muscle, cardiac muscle, kidney and red cells, and within the hepatocyte it sits in both cytosol and mitochondria. Their ratio therefore carries information about the type of injury, not just its presence.
Alcohol produces the classic elevated ratio. Chronic alcohol use depletes pyridoxal-5-phosphate, which ALT synthesis requires more than AST, and alcohol preferentially damages mitochondria, releasing the mitochondrial AST isoenzyme. The result is a ratio above 2 with both enzymes usually under 300 U/L.
In fatty liver disease the ratio starts below 1 and rises as fibrosis advances, and a reversal to above 1 in a patient with known steatosis is a recognised signal to calculate a formal fibrosis index. A high ratio with a normal or near-normal ALT should prompt a creatine kinase — the AST may not be coming from the liver at all.
Frequently asked questions
What does an AST/ALT ratio above 2 mean?
Most often alcohol-related liver injury, particularly when GGT is also raised and both transaminases are below 300 U/L. It is also seen in cirrhosis of any cause, and with a muscle source of AST.
Is a low AST/ALT ratio normal?
A ratio below 1 is usual in health and in early fatty liver or chronic viral hepatitis. It describes the pattern of injury rather than its absence — the absolute values matter too.
Why does the ratio rise as cirrhosis develops?
Sinusoidal clearance of AST falls and the mitochondrial isoenzyme is released as hepatocytes are lost, so AST declines more slowly than ALT as the liver becomes fibrotic.
Can muscle raise the ratio?
Yes. AST is abundant in skeletal muscle, so rhabdomyolysis, strenuous exercise, myositis and muscular dystrophy all raise AST with a normal ALT. Check creatine kinase before attributing it to the liver.
Related calculators
References
- De Ritis F, Coltorti M, Giusti G. An enzymic test for the diagnosis of viral hepatitis. Clin Chim Acta. 1957;2(1):70–4.
- Botros M, Sikaris KA. The de Ritis ratio: the test of time. Clin Biochem Rev. 2013;34(3):117–30.