AST (aspartate aminotransferase) is an enzyme found in the liver, skeletal muscle, heart, and red blood cells. Unlike ALT, which is more liver-specific, AST elevation is less specific for liver disease alone and can indicate injury to other tissues.
The AST:ALT ratio provides key diagnostic information: a ratio above 2:1 is characteristic of alcohol-related liver disease, while below 1:1 is typical of fatty liver and viral hepatitis. Elevated AST with normal ALT points toward cardiac or skeletal muscle injury rather than liver disease.
FAQs
What is the difference between AST and ALT?
ALT is more liver-specific than AST. AST is found in the liver, muscle, heart, and red blood cells and can rise from non-liver causes. The AST:ALT ratio is key: above 2:1 suggests alcohol-related liver disease; below 1:1 suggests fatty liver or viral hepatitis.
Can exercise raise AST?
Yes — strenuous exercise causes significant AST elevation from skeletal muscle. After intense training or endurance events, AST can remain elevated for several days. Avoid strenuous exercise for at least 48–72 hours before testing.
What does high AST with normal ALT mean?
AST elevation with normal ALT suggests a non-hepatic source — most commonly skeletal muscle injury, cardiac injury, or haemolysis. CK measurement helps confirm muscle injury.
How quickly does AST normalise after stopping alcohol?
With complete abstinence, AST typically begins falling within days and can normalise within 2–6 weeks in early liver disease. In established cirrhosis, normalisation takes longer and may be incomplete.
