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AST / ALT Ratio

The AST/ALT ratio compares two liver enzymes and helps tell whether raised values come from your liver or your muscles.

What is AST / ALT Ratio?

The AST/ALT ratio compares two liver enzymes with slightly different tissue profiles. AST is present in liver, muscle, and heart. ALT is more selective for liver tissue. The ratio helps indicate whether a rise in liver enzymes is more likely from the liver or from muscle. The ratio only carries meaning when AST or ALT are actually abnormal. With both enzymes in range, the ratio adds nothing. It remains a supporting tool — the absolute values, GGT, bilirubin, ALP, and clinical context remain primary.

Why is AST / ALT Ratio relevant?

A lower ratio has traditionally been associated with lifestyle-related liver stress. A higher ratio was classically linked to alcohol-related liver damage. In practice, that line is less clear-cut: heavy training, muscle injury, and certain muscle conditions can push AST up strongly without any liver involvement. The ratio is only useful alongside the full liver enzyme pattern. GGT is the key additional marker: with a liver source, GGT tends to rise alongside the enzymes; with a purely muscle source, GGT stays near normal.

AST / ALT Ratio high or low — what it means

Only look at the ratio if AST or ALT are actually outside the reference range. Check whether heavy training may have inflated AST — if so, the ratio says little about the liver. Use the ratio as a supplement to the full liver enzyme picture, never as the sole basis for a conclusion. A persistently elevated ratio across repeated measurements, combined with other raised liver markers, deserves medical attention.

AST / ALT Ratio reference ranges

Healthy / normalIn healthy people AST and ALT are roughly equal; the ratio sits around 1, often just below. Only meaningful when AST or ALT are actually abnormal.approx. 0.8 - 1.2 ratio
Ratio < 1Classically points more toward lifestyle/metabolic liver load (fatty liver) or acute viral hepatitis — ALT predominates.< 1 ratio
Ratio > 2A ratio of 2:1 or higher classically fits alcohol-related liver damage, especially with elevated GGT. A high ratio can also reflect muscle damage or advanced liver disease.> 2 ratio

These are interpretive guide values, not a strict normal range — there is no universal cutoff for the AST/ALT ratio (the De Ritis ratio). Cutoffs differ by lab and method, and age, sex, muscle mass and recent training all shift the ratio. The ratio is only meaningful when AST or ALT themselves are abnormal; always read it alongside the full liver enzyme pattern (ALT, AST, GGT, bilirubin, ALP).

Educational information only — not medical advice. Consult a healthcare professional for clinical decisions.

Read about our scientific approach →

Frequently asked questions

What is a normal AST/ALT ratio?

In healthy people AST and ALT are roughly equal, so the ratio sits around 1 (roughly 0.8-1.2), often just below 1. There is no hard cutoff like there is for haemoglobin or sodium — the ratio only carries meaning when AST or ALT are actually outside the reference range. If both sit comfortably within range, the ratio says little.

What does a low AST/ALT ratio (below 1) mean?

A ratio below 1 means ALT predominates. Most forms of liver injury raise ALT more than AST, so a ratio below 1 is in fact very common. Classically this points more toward lifestyle- or metabolic-related liver load, such as fatty liver, or toward acute viral hepatitis. On its own it is not a diagnosis — the absolute AST and ALT values, GGT and bilirubin remain primary.

What does a high AST/ALT ratio mean?

A ratio above 1 means AST predominates. A ratio of 2:1 or higher classically fits alcohol-related liver damage, especially when GGT is also elevated. But AST is also present in muscle and heart tissue, so heavy training or muscle damage can artificially lift the ratio without any liver involvement. With a liver source GGT rises alongside; with a purely muscular cause GGT stays near normal.

When is an abnormal AST/ALT ratio concerning?

A one-off skewed ratio is usually not worrying, especially after recent intensive training. A persistently elevated ratio across repeated measurements, together with raised liver enzymes (ALT, AST, GGT, bilirubin), deserves medical attention: a ratio that climbs toward or above 1 (from around 1.5) is associated with advanced liver damage such as fibrosis or cirrhosis. Never judge the ratio in isolation — always within the full picture and preferably after a repeat measurement under comparable conditions.

Related biomarkers

ALT
ALT is a liver enzyme that leaks into the blood when liver cells are damaged and serves as the standard marker for your liver.
AST
AST is an enzyme in liver, heart and muscle that leaks into your blood when those cells are damaged.
Gamma-GT
Gamma-GT is a liver and bile-duct enzyme that reacts sensitively to alcohol, fatty liver, and medication.
Bilirubin
Bilirubin is the yellow breakdown product of red blood cells that your liver clears through bile.

AST / ALT Ratio is one of the biomarkers in the Optimize blood test. Book a blood draw at any of 238+ partner labs in the Netherlands, or upload your existing results in the app.

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