AST Test
Also known as: Aspartate Aminotransferase, SGOT, Aspartate Transaminase
What is AST?
AST (aspartate aminotransferase) is an enzyme found in the liver, heart, muscles, and other tissues. When these tissues are damaged, AST is released into the bloodstream.[MedlinePlus (NIH)]
What This Test Measures
This test measures the level of AST enzyme in your blood. It is often used alongside ALT to assess liver health.[Mayo Clinic]
Why It's Important
AST helps detect liver damage, though it is less specific to the liver than ALT since it is also found in heart and muscles.[MedlinePlus (NIH)]
The AST/ALT ratio can help identify the cause of liver disease (ratio >2 suggests alcoholic liver disease).[Cleveland Clinic]
Who Should Get This Test?
AST is commonly ordered alongside ALT as part of liver function assessment.
Risk Factors
- Routine health screening (part of liver panel or CMP)
- Heavy alcohol use
- Suspected liver disease or hepatitis
- Taking medications that affect liver
- History of heart disease (AST also elevated in heart attack)
- Muscle disorders or recent intense exercise
- Monitoring existing liver conditions
- Unexplained fatigue or jaundice
- Obesity or metabolic syndrome
- Diabetes
Screening Schedule
Often included in routine annual bloodwork. More frequent testing for those with liver conditions or on hepatotoxic medications.
What Happens During the Test
A blood sample is drawn from a vein in your arm. AST is typically measured alongside ALT as part of a liver panel.
Duration
5 minutes for the blood draw; results usually available within 24 hours
Discomfort Level
Minimal - brief pinch from needle insertion
Risks & Side Effects
AST testing through blood draw carries very few risks.
- •Minor pain or bruising at the needle site
- •Slight bleeding
- •Rarely, lightheadedness
- •Very rare risk of infection
Normal Range
10 to 40 units per liter (U/L).
Note: Normal ranges may vary between laboratories.
Source: MedlinePlus (NIH)Unit Conversion
Convert between U/L and µkat/L
| U/L | µkat/L |
|---|---|
| 10 | 0.17 |
| 20 | 0.33 |
| 40 | 0.67 |
| 60 | 1 |
| 80 | 1.34 |
| 100 | 1.67 |
High Values
High AST can indicate liver damage, heart attack, muscle injury, or certain medications. Very high levels suggest acute liver injury.[Mayo Clinic]
Low Values
Low AST levels are generally not a concern.[Cleveland Clinic]
Test Limitations & Accuracy
AST is less liver-specific than ALT and has important limitations.
- ⚠Found in heart, muscle, kidney, and brain - not liver-specific
- ⚠Elevated after heart attack or muscle injury
- ⚠Strenuous exercise can raise AST
- ⚠Hemolysis (broken red blood cells) falsely elevates AST
- ⚠Normal AST does not rule out liver disease
- ⚠Cannot determine severity or type of liver damage alone
- ⚠Needs to be interpreted with ALT (AST/ALT ratio)
Alternative & Complementary Tests
AST is typically part of a comprehensive liver evaluation.
More liver-specific; always ordered together
To assess bile duct problems
To assess liver excretory function
To confirm liver source vs bone for elevated ALP
To determine if AST elevation is from muscle damage
To rule out heart attack if AST elevated
Frequently Asked Questions
What is the difference between AST and ALT?
ALT is more specific to the liver, while AST is also found in heart, muscles, and other organs. When both are elevated, the ratio helps determine the cause. ALT > AST often suggests fatty liver; AST > ALT suggests alcoholic liver disease.
Source: Mayo ClinicReferences
Related Condition Guides
Medical Disclaimer
This information is for educational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for interpretation of test results and medical decisions.
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