ALT vs AST — what's the difference?
ALT is liver-specific. AST is found in liver, muscle, heart, and red cells. An ALT > AST pattern suggests NAFLD; AST > ALT suggests alcohol or muscle source.
Full answer
ALT and AST are both transaminases used to assess liver function, but they have different tissue distributions. ALT is highly liver-specific. AST is found in liver, skeletal muscle, cardiac muscle, kidney, and red blood cells — making it less specific. The ratio matters: ALT > AST is the typical pattern in NAFLD and most chronic liver disease; AST > ALT (especially >2:1) raises suspicion for alcohol-related liver disease or muscle source. Intense exercise and muscle injury can elevate AST without indicating liver disease. oMeds provider review interprets the ALT/AST ratio in metabolic and lifestyle context.
Educational. Not a substitute for individualized provider review.
- ALT — Primary source · oMeds
- Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-05-29