Aspartate aminotransferase (AST) is an enzyme found in various parts of the body. The highest concentrations are found in muscle, heart, and liver. A small amount of AST is typically found in the bloodstream. Elevated amounts of this enzyme may signal a health problem.
The AST test measures the amount of AST in your blood. Other names for the test include:
- serum glutamic-oxaloacetic transaminase
The AST test is commonly used to check for liver diseases. It is usually measured together with alanine aminotransferase (ALT). The AST to ALT ratio can help your doctor diagnose liver disease.
Symptoms of liver disease that may cause your doctor to order an AST test include:
- loss of appetite
- nausea or vomiting
- swelling in the abdomen
- yellow skin or eyes (jaundice)
- dark urine
- severe skin itching (pruritus)
This test may also be ordered for people at high risk of developing liver problems. Some things that increase risk include:
- exposure to viruses that cause hepatitis
- heavy alcohol use
- family history of liver disease
- being overweight
The AST test can also be used to monitor a known liver disorder. It can be used to check treatment efficacy as well.
Finally, AST testing can be used to make certain that medications are not causing liver damage. If liver damage occurs, your doctor will be able to change your drugs.
The AST test is performed on a blood sample. Your blood will be taken by a nurse or lab technician. It is usually taken from a vein in your arm or hand, using a small needle. The blood will be collected in a tube and sent to a lab for analysis. Your doctor will inform you about your results when they become available.
No special preparations are needed for the AST test.
Risks of the AST test are minimal. You may experience some discomfort when the blood sample is drawn. There may be pain at the puncture site before or after the test.
Other potential risks of a blood draw include:
- difficulty obtaining a sample, resulting in multiple needle sticks
- excessive bleeding at the needle site
- fainting as a result of blood loss
- accumulation of blood under the skin, known as a hematoma
- infection at the puncture site
AST test results will vary based on the laboratory completing the analysis. Talk to your doctor about your results. Typically, the normal range for the AST test is 10 to 34 IU/L (international units per liter). Levels of AST greater than 10 times the normal limit usually indicate a viral hepatitis infection.
More moderate increases in AST levels may occur if you have:
- chronic viral hepatitis
- blockage of the bile duct
- cirrhosis of the liver
- liver cancer
- kidney failure
- hemolytic anemia
- inflammation of the pancreas (pancreatitis)
AST levels may also increase after a heart attack or strenuous activity. AST levels typically decline during pregnancy.