What it measures
Aspartate aminotransferase (AST) is an enzyme found in the liver, heart, muscles and red blood cells. It rises when any of these is damaged, so it is less specific to the liver than ALT and is usually read alongside it.
Why people test it
- Part of many liver function tests, read with ALT, as the balance between the two helps point to a cause.
- Checked when liver disease, including alcohol-related liver disease, is suspected.
- Monitored in people on medicines that can affect the liver.
- Rises after heavy lifting or hard endurance exercise because muscle releases AST, often for several days.
Typical range
Ranges vary between labs with the method used, age and sex, and your report shows the lab's own range. One NHS trust's lab uses below 35 U/L for adults. Source: Leeds Teaching Hospitals NHS Trust: Blood Sciences Reference Range Database v3.20.
Finger-prick or vein?
A finger-prick sample is usually fine. AST is also found in red blood cells, so a sample that breaks down (haemolyses) on the way to the lab can read falsely high.