AST ALT Ratio Calculator

The AST/ALT ratio, also called the De Ritis ratio, compares two liver enzymes from a routine blood test: aspartate aminotransferase (AST) and alanine aminotransferase (ALT). It shows which enzyme is higher and by how much. Doctors read it as a clue to the pattern behind raised liver enzymes, not as a diagnosis.

What the AST/ALT Ratio Measures

ALT is found mainly in the liver, so it is the more specific sign of liver cell injury⁴. AST is in the liver too, but also in heart muscle, skeletal muscle, the kidneys, the brain and red blood cells⁴ ⁵. The ratio shows the balance between the two. It does not measure how well your liver works, how much fat it holds, or how much scarring it has.

The Formula

AST/ALT ratio = AST ÷ ALT

Both values in the same unit (U/L, IU/L or µkat/L)

De Ritis and colleagues first compared the two enzymes this way in 1957, as a test for viral hepatitis¹.

How This Calculator Computes Your Result

Enter AST and ALT from the same blood test, in U/L (the same number as IU/L) or µkat/L. Older reports may call them SGOT and SGPT. The ratio has no unit, so the unit you pick does not change it. The ratio is rounded to two decimals, and the pattern is set from that rounded number.

The tool also checks each enzyme against a reference value. For AST it uses 33 U/L, the top of a typical normal range⁷. For ALT it uses the healthy upper limit suggested by the American College of Gastroenterology (ACG): 33 U/L for men and 25 U/L for women⁴. Sex is optional and does not change the ratio. If you leave it blank, the ALT check uses 33 U/L. A note appears if only AST is raised, or if either value is above 300 U/L. Labs set their own ranges, so go by your report if it differs⁴.

What Your Result Means

Your ratio falls into one of three patterns. The last column applies only when at least one enzyme is raised⁴ ⁵.

A ratio of 2 or more is the classic pattern of alcohol-related liver disease, described by Cohen and Kaplan in 1979². The ACG guideline notes that about 90% of people with alcohol-related liver disease have AST above ALT, and more than 70% have a ratio above 2⁴. A ratio above 3 makes the alcohol pattern more likely still, and in this disease AST and ALT rarely go above 300 U/L⁴. Much of the reason is a lack of vitamin B6 (pyridoxine), which lowers ALT activity more than AST⁴.

These patterns overlap. One review reports mean ratios of 0.9 in nonalcoholic steatohepatitis (an inflamed form of fatty liver disease) and 2.6 in alcohol-related liver disease, but warns that the groups overlap too much to diagnose from the ratio alone⁵.

Why the Ratio Means Little When Both Values Are Normal

The patterns above describe raised enzymes. When both are normal, small numbers make the ratio swing widely. AST 24 U/L and ALT 12 U/L give a ratio of 2.00, though both values are normal. Using the MedlinePlus normal ranges (AST 8 to 33 U/L, ALT 4 to 36 U/L), two normal results can give any ratio from 0.22 to 8.25⁷ ⁸. That is why this tool shows a note, not a pattern meaning, when both enzymes are within the reference values.

Doctors also look at how high each value is. The ACG grades a rise by how many times it is above the upper limit: under 2 times is borderline, 2 to 5 times is mild, 5 to 15 times is moderate, and over 15 times is severe⁴. Its healthy ALT limits (29 to 33 U/L for men, 19 to 25 U/L for women) come from large studies of healthy people⁴.

Other Reasons AST Can Be Higher Than ALT

Because AST is found outside the liver, a high ratio does not always point to the liver. The ACG notes that a rise in AST without a rise in ALT suggests heart or muscle disease. It adds that muscle breakdown (rhabdomyolysis) and heat stroke can push AST very high, and lists breakdown of red blood cells (hemolysis) among non-liver causes⁴. Hard exercise and muscle disease can raise enzymes, especially AST, without causing other symptoms⁵. MedlinePlus also lists heart attack, muscle injury, pancreatitis, mononucleosis, seizures, surgery and burns⁷.

The Ratio and Liver Scarring

In long-term liver disease, the ratio tends to be higher once scarring is advanced. The ACG notes that AST above ALT can be seen in cirrhosis of any cause, though the ratio is usually not above 2. In one study it cites, the mean ratio was 0.60 in people without cirrhosis and 1.05 in people with it⁴. Williams and Hoofnagle described this link with cirrhosis in chronic hepatitis in 1988³. In fatty liver disease, one review reports a mean ratio of 1.4 in people whose disease had reached cirrhosis⁵. In a study of 145 adults with biopsy-confirmed fatty liver disease, 93% of those with a ratio below 0.8 did not have advanced fibrosis⁶.

For a fuller estimate of scarring, our FIB-4 Calculator adds your age and platelet count to AST and ALT.