AST (Aspartate Aminotransferase)

What is AST?

AST (aspartate aminotransferase), also known as SGOT, is an enzyme found in several organs, with the highest concentrations in the liver and heart. Smaller amounts exist in muscles, kidneys, and brain.

When cells containing AST are damaged, the enzyme leaks into the bloodstream. Elevated AST levels indicate tissue damage somewhere in the body — most commonly the liver.

AST is almost always tested alongside ALT, another liver enzyme. Comparing the two helps pinpoint the source of the problem.

Normal Ranges

Group	AST Level
Adult men	10–40 U/L
Adult women	9–32 U/L

Normal ranges vary between laboratories. Mild elevations are common and not always concerning.

Why It Matters

Liver Health Assessment

AST, combined with ALT, helps detect liver damage from various causes: fatty liver, hepatitis, medication effects, or alcohol use.

Heart and Muscle Damage

Unlike ALT, AST is also elevated in heart attacks and muscle injuries. This is why doctors look at the AST/ALT ratio and other markers to determine the source.

Monitoring Medication Effects

Many medications can affect the liver. Regular AST monitoring helps catch problems early in people taking potentially liver-toxic drugs.

AST vs. ALT

Both are liver enzymes, but they differ in specificity:

ALT is more specific to the liver
AST is found in multiple organs

The AST/ALT ratio provides diagnostic clues:

Ratio < 1: Often fatty liver or viral hepatitis
Ratio > 2: Suggests alcoholic liver disease

What Affects AST

Alcohol consumption — Can significantly elevate AST
Intense exercise — Muscle breakdown releases AST
Medications — Statins, acetaminophen, others
Obesity — Associated with fatty liver
Recent muscle injury — Raises AST more than ALT

High AST Causes

Fatty liver disease
Viral hepatitis (A, B, C)
Alcoholic liver disease
Medication toxicity
Heart attack (elevated with other cardiac markers)
Muscle damage or intense exercise

How Often to Test

Routine checkups: Often included in metabolic panels
Taking liver-affecting medications: Every 3–6 months
Known liver conditions: As directed