AST (Aspartate Aminotransferase)

What is AST?

AST (Aspartate Aminotransferase) is an enzyme found primarily in liver cells, but also in heart muscle, skeletal muscle, kidneys, brain, and red blood cells. When these tissues are damaged, AST is released into the bloodstream, making it a useful marker for detecting tissue injury. While often called a “liver enzyme,” AST isn’t specific to liver damage alone.

Why is it Tested?

Doctors order AST to evaluate liver function and detect liver damage, often alongside ALT (alanine aminotransferase) as part of a liver panel. It’s also used to monitor the effects of medications that can affect the liver, assess unexplained abdominal symptoms, and evaluate people with risk factors for liver disease such as alcohol use, hepatitis, or certain medications.

Normal Ranges

What do Abnormal Results Mean?

Abnormal results are not a diagnosis. Always discuss your results with a qualified healthcare provider before making any medical decisions.

Low AST

Low AST levels are generally not concerning and rarely indicate any medical problem. Very low levels might occasionally be seen with certain vitamin deficiencies but are typically considered normal variants.

High AST

Elevated AST levels may indicate tissue damage and possible causes include:

• Liver diseases (hepatitis, fatty liver, cirrhosis)
• Heart muscle damage (heart attack)
• Muscle injury or disease
• Certain medications or supplements
• Alcohol use
• Bile duct obstruction

How to Track Over Time

Monitoring AST trends helps evaluate liver health changes and treatment responses. The AST/ALT ratio can provide additional diagnostic clues — ratios above 2:1 may suggest alcoholic liver disease, while ratios closer to 1:1 often indicate viral hepatitis or non-alcoholic fatty liver disease. Serial measurements are more informative than single values.