AST/ALT Ratio Calculator (De Ritis Ratio)
The De Ritis ratio divides two liver enzymes from the same standard panel: AST ÷ ALT. Each enzyme alone tells you liver cells are irritated; their ratio adds a hint about the pattern behind it, because AST and ALT live in different amounts inside and outside the liver. It is one of the oldest computed markers in clinical chemistry — and one of the most misread.
From the same blood draw as ALT
From the same blood draw as AST
Enter your values above to see your results.
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How it works
The formula
AST/ALT ratio = AST ÷ ALT, both in U/L from the same blood draw. First described by Fernando De Ritis in 1957, it remains one of the most-cited computed markers in liver panels. No unit conversion is ever needed.
The most important caveat: normal enzymes
The ratio was derived to compare patterns of elevated enzymes. When both AST and ALT are comfortably within their reference ranges, the ratio carries little to no clinical meaning — a 'high' ratio made of two normal numbers is usually just noise. Interpret the ratio only in the context of the absolute enzyme values.
Why the ratio behaves the way it does
ALT is concentrated in liver cells, so liver-cell irritation releases relatively more ALT (ratio below 1). AST also lives in heart, muscle, kidney, and red blood cells — so muscle damage, hemolysis, and intense exercise all raise AST without touching the liver. The alcohol-related pattern (ratio above 2) is thought to reflect B6-related ALT synthesis differences plus mitochondrial AST release.
Evidence level & limitations
The ratio's associations are research-cohort patterns described over decades — they are not diagnostic criteria for any condition, and major guidelines do not use the ratio as a standalone tool. This page offers pattern education from routine labs: a screening signal, not a diagnosis, and never a substitute for clinical evaluation.
De Ritis ratio quick reference
Pattern readings for the AST/ALT ratio, assuming a fasting draw and no recent intense exercise. Research-cohort conventions — meaningful mainly when one or both enzymes are elevated.
| AST/ALT ratio | Reading | Common context |
|---|---|---|
| < 1 | ALT-dominant | Most common pattern in healthy cohorts; classic in hepatocellular (liver-cell) enzyme elevations |
| 1 – 2 | AST-dominant | Appears in healthy people too; in research cohorts associated with more advanced liver patterns; check for muscle sources |
| ≥ 2 | Markedly AST-dominant | Classically studied in alcohol-related patterns; also muscle-derived AST and other causes — pattern reference, not a diagnosis |
A screening signal, not a diagnosis. When both enzymes are within range, the ratio has little meaning — absolute values come first.
Frequently asked questions
How do I calculate my AST ALT ratio?
Divide AST by ALT using the values from the same blood draw — both are on any standard liver or comprehensive metabolic panel. Example: AST 32 U/L with ALT 28 U/L gives a ratio of about 1.14. The calculator above does it instantly.
What is a normal AST ALT ratio?
In healthy adult cohorts the ratio typically sits a little below 1 (ALT slightly higher than AST). There is no official reference range for the ratio itself — labs report reference ranges for each enzyme separately, and those absolute values matter far more than their ratio.
Does the AST ALT ratio matter if my levels are normal?
Mostly no. The ratio was designed to compare patterns of elevated enzymes. When both AST and ALT are within their reference ranges, the ratio adds little — a ratio that looks 'high' can be produced by two perfectly normal numbers. Focus on the absolute values; bring the ratio in only when one or both are elevated.
What does an AST ALT ratio above 2 mean?
In research cohorts, a ratio above 2 has been classically associated with alcohol-related liver patterns — but it is not specific: intense exercise, muscle injury, hemolysis, and other causes raise AST from outside the liver and can produce the same ratio. It is a pattern reference that needs clinical context, not a diagnosis of anything.
Can intense exercise affect this ratio?
Yes — meaningfully. Muscle contains large amounts of AST, so a hard training block or a single heavy session in the days before your draw can raise AST (and therefore the ratio) without any liver involvement. If your AST is up with a normal ALT and recent hard exercise, retesting after a rest week is a common-sense step to discuss with your practitioner.
Is a high or low AST ALT ratio a diagnosis?
No. The ratio is a pattern signal computed from routine labs — associations described in research cohorts, not diagnostic criteria. Any ratio, in either direction, is a prompt for context (absolute values, symptoms, history, possibly further testing) with a qualified practitioner.
Sources
- Botros M, Sikaris KA. The De Ritis ratio: the test of time. Clin Chem Acta, 2013.
- Sorbi D, Boynton J, Lindor KD. The ratio of aspartate aminotransferase to alanine aminotransferase: potential value in differentiating nonalcoholic steatohepatitis from alcoholic liver disease. Am J Gastroenterol, 1999.
This calculator is for informational purposes only and is not medical advice, diagnosis, or treatment. Reference ranges are general population guidelines — always discuss your lab results with a qualified healthcare professional.