AST, aspartate aminotransferase, is an enzyme found inside cells, most abundantly in liver, heart, and skeletal muscle. Blood levels rise when those cells are damaged and their contents leak out, so the test speaks for tissue injury rather than for how well the liver is doing its work. It is one of the standard liver enzymes on a routine panel.
No readings for this marker yet.
Raised values most often follow liver cell injury, from fatty liver disease, alcohol, viral hepatitis, or a drug the liver is metabolising. Because the enzyme is also plentiful in muscle, a rise can equally come from heavy exercise, a muscle injury, or heart muscle damage, which is why an isolated elevation is not by itself a liver finding. Low values have no clinical meaning. A single raised result is a reason to repeat the test and discuss it with a doctor, not a conclusion.
Strenuous exercise in the preceding days, a recent intramuscular injection, and haemolysis during blood collection all raise the number without any liver involvement. Alcohol in the days before the draw and several common medicines, including paracetamol and non-steroidal anti-inflammatories, are the usual reasons this enzyme is watched. It is interpreted with ALT, whose ratio to AST helps separate liver from muscle, and alongside GGT, alkaline phosphatase, and bilirubin.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.