Explainer · updated 2026-11-09
AST, explained in plain English
Key facts
- Typical adult reference interval: 11-34 U/L (HRI-HR)
- What AST is: an enzyme found in liver cells, and also in muscle and heart, so it is less specific to the liver than ALT (ACG 2017)
- What a hard workout does to it: can raise it for days without anything being wrong with the liver (ACG 2017)
- What a low AST means: no liver meaning, though in older people it tracks frailty and loss of muscle (ACG 2017)
What it is
AST stands for aspartate aminotransferase. It is an enzyme found in liver cells, and also in muscle and heart, so it is less specific to the liver than the ALT beside it. The two are read together, and the pattern between them carries the meaning. It is measured in the blood.
What the number is telling you
A raised AST tells your doctor that cells are leaking, from the liver or from muscle. The size of the rise, the other liver results beside it and the trend over time all matter. A hard workout can raise it for days without anything being wrong with the liver.
What high or low can mean
High: Liver cells leaking, or muscle. Alcohol and fat in the liver raise both AST and ALT, and both fall when those come down. Where the rise comes from is for your doctor to say.
Low: A low figure carries no liver meaning, though in older people it tracks frailty and loss of muscle.
What a typical result looks like
The harmonized adult interval from the HRI-HR set, verified in Croatia and published in Biochemia Medica in 2026, runs from 11 to 34 U/L. The range on your own report is the one that counts.
Questions worth asking your doctor
- How does my AST compare with my ALT?
- Could exercise explain this reading?
- What do the other liver results add to the picture?
- How does this compare with my previous results?
If a result worries you, ask your doctor.
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