What this calculator does
AST and ALT are enzymes released when liver cells are damaged. ALT is found mostly in the liver while AST is also present in muscle, heart and red blood cells, and the ratio between them carries information the individual values do not.
Fernando De Ritis described the pattern in 1957. A ratio below 1 is more typical of viral hepatitis and fatty liver disease, while a ratio above 2 has long been associated with alcohol-related liver injury.
The formula
Divide AST by ALT, both in U/L from the same sample. The result is a plain ratio read against conventional bands.
| Term | Meaning |
|---|---|
| AST | Aspartate aminotransferase, present in liver, muscle, heart and red cells. |
| ALT | Alanine aminotransferase, more specific to the liver. |
| De Ritis ratio | AST divided by ALT, named for the researcher who described the pattern. |
The inputs explained
| Field | What to enter |
|---|---|
| AST (U/L) | AST in U/L from a liver function panel. |
| ALT (U/L) | ALT in U/L from the same sample. |
When to use it
Reading a liver panel
The ratio adds a pattern that neither enzyme alone provides.
Following a trend
A shifting ratio over time can be more informative than either value in isolation.
Understanding a referral
The ratio is one of the factors that shapes which further tests are ordered.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What does each AST level give?
The same ALT at four AST levels.
| AST | AST-to-ALT ratio | Reading |
|---|---|---|
| 15 U/L | 0.60 | Below 1: more typical of viral hepatitis or fatty liver disease |
| 25 U/L | 1.00 | Between 1 and 2: nonspecific |
| 50 U/L | 2.00 | Above 2: can suggest alcohol-related liver disease |
| 75 U/L | 3.00 | Above 2: can suggest alcohol-related liver disease |
Questions
Is a ratio above 2 diagnostic of alcohol-related liver disease?
No. It is a recognised pattern, not a diagnosis, and it has significant exceptions in both directions. Diagnosis requires history, examination and other investigations, and the pattern only suggests where to look.
Why can AST rise without liver disease?
Because AST is also present in skeletal muscle, heart muscle and red blood cells. Vigorous exercise, muscle injury and haemolysis can all raise it, which shifts the ratio without any liver involvement at all.
Does the ratio matter if both values are normal?
Much less. The bands were described in the context of raised enzymes, and a ratio computed from two normal values carries little information. Both absolute values and the ratio should be read together.
What is the FIB-4 score?
A related index that combines AST, ALT, platelet count and age to estimate liver fibrosis. It is more widely used clinically than the De Ritis ratio alone for that particular question.
For the kidney marker pattern, see the BUN-to-creatinine ratio calculator. For protein balance in blood, see the albumin-to-globulin ratio calculator.