What is AST?
Aspartate aminotransferase (AST) is an enzyme found in the liver but also in muscle, heart, and red blood cells. Because it is less liver-specific than ALT, AST is interpreted together with ALT the AST:ALT ratio helps distinguish causes such as alcohol-related liver disease from other injury.
Why it matters
AST complements ALT in evaluating liver injury. A high AST:ALT ratio (over 2) suggests alcohol-related liver disease, while AST elevation without liver cause may point to muscle injury.
What it measures
The blood concentration of AST, interpreted with ALT and the AST:ALT ratio.
Reference & optimal ranges
Reference ranges vary by lab, assay, age, and sex. The ranges below reflect commonly published adult intervals and are for education only always interpret results with the range printed on your own lab report and a clinician.
High AST reflects liver injury or, when out of proportion to ALT, muscle or other tissue damage.
Common symptoms
- Often none
- Fatigue
- Muscle soreness (if muscle source)
- Jaundice (advanced liver disease)
Potential causes
- Fatty liver disease
- Alcohol-related liver disease (high AST:ALT)
- Viral hepatitis
- Muscle injury or intense exercise
- Medications
- Heart injury
Low AST is not clinically significant.
Common symptoms
- None
Potential causes
- Normal variation
How to improve your AST
Lifestyle
Limit alcohol
A high AST:ALT ratio often reflects alcohol; reducing intake helps.
Nutrition
Weight loss for fatty liver
Reducing added sugar and excess weight improves liver enzymes.
Exercise
Time testing around exercise
Intense exercise can transiently raise AST from muscle; avoid heavy workouts before testing.
Sleep
General health
Supports overall metabolic and liver health.
Frequently asked questions
Scientific references
Educational information, not medical advice. This page is for general education and does not replace diagnosis or treatment by a licensed clinician. Do not start, stop, or change any medication, supplement, or treatment based on this content. Reference and optimal ranges vary between laboratories interpret your results with the range on your own report and a qualified professional.