What is the AST:ALT ratio?
AST (aspartate aminotransferase, also called SGOT) and ALT (alanine aminotransferase, also called SGPT) are liver enzymes measured in every liver function test. While both rise when liver cells are damaged, they rise to different degrees depending on the cause. The AST:ALT ratio — also called the De Ritis ratio — is calculated by dividing the AST value by the ALT value. The pattern of which enzyme rises more provides a diagnostic clue to the underlying cause of liver damage.
AST:ALT ratio interpretation
| Ratio | Pattern | Likely diagnosis |
|---|---|---|
| < 1 (ALT > AST) | ALT dominant | Viral hepatitis (A, B, C), NAFLD/fatty liver, drug-induced liver injury |
| 1:1 | Equal rise | Non-specific — less diagnostic value |
| > 2:1 (AST 2x ALT) | AST dominant | Alcoholic liver disease (classic pattern) |
| > 3:1 | Strongly AST dominant | Alcoholic hepatitis or cirrhosis; consider Wilson disease |
| Very high ALT (10x+), any ratio | Massive elevation | Acute viral hepatitis, ischaemic hepatitis, drug toxicity |
Why is AST:ALT >2 typical of alcoholic liver disease?
In alcoholic liver disease, alcohol and its metabolite acetaldehyde directly damage mitochondria (where AST is concentrated in liver cells), causing disproportionate AST release. Simultaneously, alcohol depletes pyridoxal-5-phosphate (vitamin B6), which is required for ALT synthesis — so ALT levels are relatively suppressed. This two-part mechanism explains why AST rises more than ALT in alcoholic liver injury.
Why is ALT higher than AST in viral hepatitis and fatty liver?
In viral hepatitis and NAFLD, hepatocyte cell membrane damage is the primary mechanism, and ALT is predominantly cytoplasmic (released easily through the damaged membrane). ALT is also more specific to the liver than AST (which also comes from heart, muscle and other tissues). So in non-alcoholic liver disease, ALT is the more sensitive and more elevated marker.
Other tests to interpret alongside the ratio
| Test | Why it matters |
|---|---|
| GGT | Very high in alcoholic liver disease; supports AST:ALT >2 pattern |
| MCV (mean cell volume) | High MCV (macrocytosis) is common with alcohol excess |
| Bilirubin | Indicates severity of liver dysfunction |
| Albumin / INR | Liver synthetic function — low = serious |
Questions to ask your doctor
- What is likely causing my liver enzyme elevation?
- Do I need a hepatitis B and C test?
- Should I have a liver ultrasound?
- Is alcohol use contributing to my liver results?
- Do I need a liver biopsy?