AST (aspartate aminotransferase) is an enzyme found in the liver, heart, skeletal muscle, kidneys, and red blood cells. Elevated AST indicates tissue damage but is less specific to the liver than ALT. The AST/ALT ratio (De Ritis ratio) helps differentiate the source of elevation.

An AST/ALT ratio less than 1 typically suggests fatty liver disease or metabolic liver damage. A ratio greater than 2 is more suggestive of alcoholic liver disease. When AST is elevated but ALT is normal, non-hepatic sources like muscle damage, intense exercise, or cardiac events should be considered.

Like ALT, standard reference ranges for AST may be set too high. Functional medicine practitioners often use tighter optimal ranges, particularly when screening for subclinical liver dysfunction or metabolic health.

What It Measures

AST measures the activity of aspartate aminotransferase enzyme in the blood. Because AST exists in multiple organs, its elevation requires context (typically comparing with ALT) to determine the source.

Reference Ranges

How GATOR Tracks This

Related Biomarkers