AST (aspartate aminotransferase) is an enzyme that helps process amino acids. It’s found in your liver, heart, and skeletal muscle. When cells in these tissues are injured, AST can rise in your blood. Because ALT is more specific to the liver, comparing the two helps determine the source of elevation.
Tip: Check the AST-to-ALT ratio. If AST is higher than ALT (especially >2:1), alcohol or muscle-related causes are more likely. ALT being higher suggests liver-specific issues.
Common reasons AST is high
- Liver inflammation or infection
- Excess alcohol use
- Muscle injury or intense exercise
- Medication or supplement side effects
- Heart injury (less common today)
- Viral hepatitis or autoimmune liver disease
How AST relates to other liver markers
- ALT: often elevated in parallel with AST in liver conditions.
- ALP and bilirubin: tend to rise in bile flow obstruction or cholestatic disorders.
- GGT: helpful to confirm liver source when AST or ALP are high.
When to repeat or discuss AST testing
- If mildly elevated, repeat in 1–3 months after addressing temporary causes (exercise, alcohol, medication).
- Persistent or marked elevations should be evaluated for chronic liver or muscle disease.
- Always review results with your clinician before changing or stopping medication.
AST High — Frequently Asked Questions
Is AST of 50 considered high?
Many labs set the upper limit of normal around 35–40 U/L. An AST value near 50 U/L is usually mildly elevated and should be interpreted together with ALT and other markers.
Can exercise raise AST levels?
Yes. Heavy workouts, muscle strain, or injury can temporarily increase AST. Retesting after a few days of rest helps clarify whether the source is muscular rather than liver-related.
When should I worry about high AST?
AST deserves closer evaluation when it is more than two to three times the normal limit, stays elevated on repeat testing, or rises together with ALT, ALP, GGT, or bilirubin.
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