Aspartate Aminotransferase (AST)
AST is an enzyme released by damaged liver, heart and skeletal-muscle cells. Less liver-specific than ALT but a key part of the routine liver panel.
What it measures
AST (also called SGOT) lives inside multiple tissues — predominantly the liver, but also heart muscle, skeletal muscle, kidney and red blood cells. When any of those tissues are stressed or damaged, AST leaks into the bloodstream. Because the source is non-specific, AST is interpreted alongside ALT: an AST/ALT ratio greater than 2 in someone without obvious muscle injury is the classic alcohol-related liver disease pattern. Both enzymes rising together points at hepatocellular injury more broadly.
What a high value can mean
- Liver injury — viral hepatitis, NAFLD, drug-induced liver injury, alcohol.
- AST/ALT ratio > 2 — classic for alcohol-related liver disease.
- Cardiac injury — historically used for myocardial infarction (troponin replaced this role).
- Skeletal muscle injury — rhabdomyolysis, recent very strenuous exercise.
- Haemolysis — red blood cells contain AST.
What a low value can mean
- Vitamin B6 deficiency — AST is pyridoxal-phosphate-dependent.
- Severe end-stage liver disease — few remaining hepatocytes.
- Generally not clinically actionable.
When to discuss with a doctor
AST elevation alongside ALT elevation warrants follow-up with the rest of the liver panel and a primary-care visit. Very-high AST without a corresponding ALT rise should prompt a check of CK (muscle injury) and the haemolysis panel. AST >1000 U/L is acute liver injury and needs same-day evaluation.