Normal range: 10 – 40 U/L (lower is better)
AST is an enzyme found in the liver, heart, and muscle. Unlike ALT (which is mostly liver-specific), AST rises with damage to any of these tissues. This makes it less precise for liver problems on its own but useful when read alongside ALT. The AST/ALT ratio (called the de Ritis ratio) helps doctors distinguish between different types of liver disease.
A normal AST is 10 – 40 U/L. Lower is better.
The same liver conditions that raise ALT also raise AST: fatty liver disease, hepatitis, alcohol use, and medications. However, AST is less liver-specific. It also rises after intense exercise (especially weight training), muscle injury, heart attacks, and in conditions like rhabdomyolysis.
Alcoholic liver disease typically produces AST higher than ALT (de Ritis ratio above 2), while non-alcoholic fatty liver shows the reverse. This pattern helps clinicians identify the underlying cause.
The same lifestyle changes that improve ALT apply here: reducing alcohol, losing excess weight, and exercising regularly. If you get a high AST after a tough workout, that is usually harmless and will normalize within a few days. Medications that can raise AST include acetaminophen, statins, certain antibiotics, and anti-seizure drugs.
AST is an enzyme found in the liver and other organs. High levels may indicate liver damage.
In NHANES 2021-2023, the median AST was about 18 U/L for adults aged 18-29 and 21 U/L for adults aged 70 and older. The chart below shows the full distribution by age and sex.
Median AST by age and sex, with the 10th to 90th percentile band. Source: NHANES 2021-2023 (weighted estimates).
AST is most highly correlated with ALT and Urine Specific Gravity. Here are the top biomarkers correlated with AST, based on 500,000 tests done by Empirical Health.
The percentage shows how strongly two biomarkers move together. A higher number means the relationship is stronger. Green = rises and falls together. Orange = one rises as the other falls.
AST comes in a comprehensive metabolic panel (about $29–$55), or $190 with ALT, ALP, and 100+ other biomarkers at Empirical Health.
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