Quick Guide: Aminotransferase, aspartate (AST) Blood Test
What it is: An AST (aspartate aminotransferase) test measures the level of AST, an enzyme found in the liver, heart, muscles, and other tissues, in a blood sample.
Why it's ordered: Ordered to assess liver health, typically alongside ALT in a liver panel, when a provider suspects liver damage, or to help evaluate other conditions affecting muscle or heart tissue.
What it detects: AST leaks into the blood when liver cells (or other AST-containing tissues, like heart or skeletal muscle) are damaged. Because AST is less liver-specific than ALT, comparing the two — the AST-to-ALT ratio — helps distinguish liver injury from other causes and can hint at alcohol-related versus other liver damage.
Collection & prep: A standard blood draw from a vein in the arm. As with ALT, no special prep is typically required unless it's part of a larger fasting panel.
Results:
High – typically above 35 IU/L in adults; suggests damage to the liver or another AST-containing tissue
Normal – roughly 0–35 IU/L, though ranges vary by lab
Possible complications of liver or muscle damage: AST alone can't pinpoint the source of damage since it's present in several organs; providers typically interpret it alongside ALT, CK, and clinical symptoms to determine whether the cause is hepatic, cardiac, or muscular.
Statements made in the Clinical Manual have not been evaluated by the FDA. The products mentioned are not intended to diagnose, treat, cure or prevent any disease.
