Aspartate Aminotransferase
AST· also: SGOT, Aspartate Aminotransferase
Clinical Overview
AST is an enzyme found in liver, heart muscle, skeletal muscle, kidneys, brain, and red blood cells. Elevated AST indicates tissue damage, most often in the liver or heart. AST is less liver-specific than ALT but is valuable when interpreted alongside ALT and other tests.
Why This Test Matters
The AST/ALT ratio is a powerful diagnostic tool. An AST:ALT ratio >2:1 (especially >3:1) with elevated GGT strongly suggests alcoholic liver disease. In myocardial infarction, AST rises alongside troponin and CK-MB. In acute hepatitis, AST and ALT often rise in parallel. AST alone is insufficient to localize damage — muscle and cardiac causes must be excluded.
Reference RangesWHO/IFCC standards
| Age Group | Sex | Reference Range | Unit | Notes |
|---|---|---|---|---|
| Adults (18–64) | Male | 10 – 40 | U/L | — |
| Adults (18–64) | Female | 10 – 35 | U/L | — |
Also reported in: IU/L.
What Causes Abnormal Results?
High AST Causes
- Liver diseases (hepatitis, cirrhosis, NAFLD) — same as ALT
- Acute myocardial infarction (MI)
- Skeletal muscle injury or rhabdomyolysis
- Strenuous exercise
- Alcoholic liver disease (typically AST:ALT >2:1)
- Hemolytic anemia (AST in RBCs released)
- Pulmonary embolism
- Hypothyroidism
Low AST Causes
- Not clinically significant
- Vitamin B6 (pyridoxine) deficiency (cofactor for AST — may falsely lower AST)
Signs & Symptoms to Watch For
How to Prepare for This Test
Avoid heavy exercise 24–48 hours before testing. No fasting required but preferred. Inform your doctor of all medications.
Factors That Can Affect Results
- Strenuous exercise (significantly raises AST from muscle)
- Intramuscular injections (raises AST)
- Hemolysis in sample (AST in red blood cells is released)
- Alcohol ingestion
- Medications: statins, paracetamol, NSAIDs
Related Topics
Frequently Asked Questions
What does an AST/ALT ratio above 2 mean?
An AST:ALT ratio above 2 (especially above 3), combined with elevated GGT, is a classic pattern of alcoholic liver disease. In alcoholic hepatitis, AST is typically elevated but rarely exceeds 300–500 U/L — very high AST in alcoholic liver disease should prompt consideration of another cause. Non-alcoholic liver diseases (viral hepatitis, NAFLD) typically have AST:ALT ratios below 1.
Can high AST come from the heart rather than the liver?
Yes. AST is found in cardiac muscle cells and rises after myocardial infarction — historically it was used to diagnose MI before troponin tests were available. Today, troponin and CK-MB are the preferred cardiac markers. If AST is elevated without corresponding ALT elevation, muscle or cardiac injury should be considered. Measuring CK (creatine kinase) helps differentiate muscle from liver sources.