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Interpretation thresholds: <1.0 = ALT dominant (viral/NAFLD pattern) | 1.0–2.0 = borderline / possible cirrhosis | ≥2.0 = strongly suggests alcoholic liver disease (De Ritis ratio)
What Is the AST/ALT Ratio and Why Does It Matter?
The AST/ALT ratio — also called the De Ritis ratio — is one of the most clinically useful calculations derived from a standard liver function test (LFT). By dividing your AST (aspartate aminotransferase) value by your ALT (alanine aminotransferase) value, physicians can distinguish between different types of liver disease with reasonable accuracy, even before imaging or biopsy.
First described by Italian physician Fernando De Ritis in 1957, the ratio has stood the test of time as a rapid, cost-free screening tool. It requires no additional testing — just two numbers already present in a routine blood panel.
Normal AST and ALT Reference Ranges
| Enzyme | Men (Normal) | Women (Normal) | Note |
|---|---|---|---|
| AST | 10–40 U/L | 10–35 U/L | Found in liver, heart, muscle, kidneys |
| ALT | 7–56 U/L | 7–45 U/L | Primarily liver-specific |
| AST/ALT Ratio | < 1.0 | < 1.0 | Normal pattern (ALT ≥ AST) |
How to Interpret Your AST/ALT Ratio
| Ratio Range | Pattern | Possible Causes |
|---|---|---|
| < 1.0 | ALT dominant | Viral hepatitis, NAFLD, drug-induced liver injury, obesity-related liver disease |
| 1.0 – 2.0 | Borderline | Cirrhosis, hepatic fibrosis, chronic liver disease (any cause), muscle disease |
| ≥ 2.0 | AST dominant | Alcoholic liver disease (De Ritis ratio), alcoholic hepatitis, advanced cirrhosis |
Why Is ALT More Specific for Liver Damage?
ALT (alanine aminotransferase) is found almost exclusively in liver cells, making it highly specific for hepatocellular damage. AST, by contrast, is present in the liver but also in cardiac muscle, skeletal muscle, kidneys, and red blood cells. This is why an isolated AST elevation without ALT elevation often points to muscle injury, heart attack, or hemolysis rather than liver disease.
The De Ritis Ratio in Alcoholic Liver Disease
Alcohol causes unique mitochondrial damage that preferentially releases AST over ALT. In alcoholic hepatitis, AST levels typically rise 2 to 8 times the upper limit of normal, while ALT rarely exceeds 300 U/L regardless of severity. This produces the characteristic De Ritis ratio above 2.0. Importantly, very high ALT (>300 U/L) in someone with suspected alcoholic liver disease should prompt evaluation for a co-existing cause such as viral hepatitis or acetaminophen toxicity.
A normal AST/ALT ratio is typically less than 1.0. Most healthy individuals have slightly more ALT than AST, making the ratio below 1. Ratios above 2.0 strongly suggest alcoholic liver disease.
A ratio above 2.0 is strongly associated with alcoholic liver disease (the De Ritis ratio). This occurs because alcohol damages mitochondria, releasing more AST relative to ALT. Ratios above 2 in the right clinical context are highly suggestive of alcoholic hepatitis.
Elevated AST with normal ALT can indicate muscle damage (AST is also in heart and skeletal muscle), hemolysis, thyroid disease, or strenuous exercise. It is less specific for liver disease than elevated ALT alone.
Yes. ALT is found primarily in the liver, making it more specific for hepatic damage. AST is found in liver, heart, skeletal muscle, kidneys, and red blood cells, so elevated AST alone is less specific for liver disease.
A ratio between 1.0 and 2.0 may indicate cirrhosis or hepatic fibrosis. As cirrhosis progresses, AST tends to rise relative to ALT because the liver loses ALT-producing hepatocytes. The ratio rising above 1.0 in a known liver disease patient warrants evaluation for fibrosis.
Yes. Statins, acetaminophen, NSAIDs, antibiotics, and herbal supplements can all elevate liver enzymes. Drug-induced liver injury typically shows elevated ALT more than AST, giving a ratio below 1.
The De Ritis ratio is another name for the AST/ALT ratio, named after Italian physician Fernando De Ritis who first described its diagnostic significance in the 1950s. A De Ritis ratio above 2 is a classic marker for alcoholic hepatitis.
A liver function test panel typically includes AST, ALT, alkaline phosphatase (ALP), GGT, total bilirubin, albumin, and total protein. The AST/ALT ratio is one key value derived from this panel.
Generally, AST or ALT values more than 3 times the upper limit of normal (ULN) are considered clinically significant. For AST, the ULN is about 40 U/L in men and 35 U/L in women. For ALT it is about 56 U/L in men and 45 U/L in women.
In non-alcoholic fatty liver disease (NAFLD), the ratio is typically less than 1 with ALT higher than AST. As NAFLD progresses to cirrhosis the ratio may exceed 1. A ratio consistently below 1 in the context of fatty liver is relatively reassuring.