Aspartate aminotransferase (AST)

Aspartate aminotransferase is an enzyme found in the liver, heart, and skeletal muscle, measured in blood as a marker of tissue injury.

Unlike ALT, which is fairly specific to the liver, AST is present in several tissues, so a rise can reflect liver stress, muscle strain, or other causes. Laboratories report AST in units per liter with a reference range, and clinicians typically read it together with ALT; the ratio between the two can hint at the source of the problem. AST is part of standard liver panels in both human medicine and veterinary practice.

AST appears in cannabinoid safety discussions because it is monitored alongside ALT in trials of prescription cannabidiol, where transaminase elevations were observed in a minority of participants, more often at higher doses or with certain concomitant medications. In canine research, AST is included in the blood chemistry checks used to track tolerability. An isolated AST result rarely tells the whole story; it is interpreted in the context of other tests, symptoms, and the substances a person or animal has been exposed to.