Two liver enzymes
AST (aspartate aminotransferase, once called SGOT) and ALT (alanine aminotransferase, once called SGPT) are enzymes released into the blood when liver cells are damaged. ALT is found mostly in the liver, while AST is also present in heart, muscle, kidney and red blood cells. Beyond the size of the rise, the AST/ALT ratio, also called the De Ritis ratio after the Italian physician who described it in 1957, gives a hint about the cause.
The formulas
- AST/ALT ratio = AST (U/L) ÷ ALT (U/L)
- Times the upper limit of normal = result ÷ upper limit of normal (ULN)
The calculator uses 40 U/L as the default upper limit; replace it with the value printed on the lab report, which is often lower for women.
Worked example
A blood test shows AST 45 U/L and ALT 60 U/L, with an upper limit of 40 U/L for both.
- Ratio = 45 ÷ 60 = 0.75, below 1.
- AST = 45 ÷ 40 = 1.1 × ULN; ALT = 60 ÷ 40 = 1.5 × ULN.
This is a mild rise with ALT predominant, a pattern frequently seen in fatty liver disease.
Interpreting the ratio
| AST/ALT | Common associations |
|---|---|
| Below 1 | Fatty liver disease (MASLD, formerly NAFLD), viral hepatitis, drug-induced liver injury |
| 1 to 2 | Nonspecific; can suggest progression to cirrhosis in chronic liver disease |
| Above 2 | Alcohol-related liver disease, especially with AST under 300 U/L |
In alcohol-related disease, AST rises more than ALT partly because alcohol depletes vitamin B6, which ALT needs. A ratio above 1 in someone with chronic hepatitis or fatty liver can also be a sign of advanced fibrosis, which is why the ratio is part of scores such as FIB-4.
Size of the rise
| Level | Typical setting |
|---|---|
| Under 5 × ULN | Fatty liver, alcohol, medicines, chronic hepatitis |
| 5 to 15 × ULN | Acute hepatitis, more marked drug injury |
| Above 15 × ULN (often over 1,000 U/L) | Acute viral hepatitis, acetaminophen overdose, shock liver |
When the ratio misleads
Intense exercise, muscle injury and hemolysis raise AST without liver disease. Very high values make the ratio less useful. Always interpret the enzymes with bilirubin, alkaline phosphatase, GGT, albumin, the platelet count and the clinical history.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.