AST

Measured in U/L

An enzyme often grouped with 'liver tests,' but it's also abundant in muscle and can rise after hard exercise, so it isn't liver-specific.

What it is

AST (aspartate aminotransferase) is an enzyme that lives inside cells and leaks into the blood when those cells are stressed or damaged. It's commonly called a liver enzyme, but it's also present in skeletal muscle, heart, and red blood cells — which is why a strenuous workout, a muscle injury, or a hemolyzed blood sample can push it up without the liver being involved. It's most meaningful read next to ALT (which is more liver-specific), along with alkaline phosphatase, bilirubin, and albumin, and single mildly elevated values are common and often rechecked rather than acted on.

Typical range

  • Male8–48 U/L
  • Female8–43 U/L

Source · Mayo Clinic Laboratories (AST) (2026)

Reference ranges vary between laboratories, and what is normal for you depends on your own history. Your own lab’s range is the one printed on your report.

Worth asking your clinician

  • Could my exercise or activity in the days before the blood draw have affected my AST?
  • How does my AST look compared with my ALT, and does that comparison tell you anything?
  • Would you want to repeat this test after a period of rest to see whether it settles?