AST Test (Aspartate Aminotransferase)
Reviewed
An AST blood test measures the amount of AST (aspartate aminotransferase) in your blood. It is commonly used to help diagnose liver damage or disease. AST is an enzyme found mainly in your liver but also in your heart, muscles, and other tissues. When liver or other cells that contain AST are damaged, they release AST into your blood, leading to high levels.
Preparation and collection
You may need to stop taking certain medicines before the test; tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to. An AST test is usually ordered with other blood tests, and you may need to fast (not eat or drink) for up to 12 hours before these tests. Your provider will let you know if there are any special instructions.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Many things can affect your results, such as pregnancy, exercise, certain medicines, and your age or sex.
- A result that is not in the normal range does not always mean that you have a medical condition that needs treatment.
- The test is not diagnostic by itself; it is often part of a group of liver function tests.
What to do next
Talk with your provider to learn what your results mean. Your provider may order an ALT blood test along with your AST test. If you have high levels of AST and/or ALT, it may mean that you have some type of liver damage.
Evidence source
U.S. National Library of Medicine: AST Test (Aspartate Aminotransferase)