Aspartate aminotransferase (AST) is an enzyme. Enzymes are types of proteins that enable most bodily processes. AST exists mostly in the liver, but it is found in numerous tissues in the body.
When cells become damaged, AST can be released into the bloodstream. For this reason, abnormal levels of AST in a blood sample can be an indication of an underlying problem.
Although AST can be measured alone, it is usually included with other enzymes as part of broader tests, such as a liver panel or comprehensive metabolic panel (CMP). When interpreted alongside other enzymes, an AST measurement can help identify the liver disease and other health issues.

Purpose of the test

A blood test measuring AST is used to detect damage to cells. Most often, it is used to help assess the condition of the liver, but it can provide insight into other health concerns as well.
Depending on the situation, AST testing, usually combined with other measurements in a panel test, can be used as a form of medical screening, diagnosis, or monitoring:

• Screening is the medical term for testing when you don’t have any symptoms of a condition. Screening that includes AST may be prescribed if you have risk factors for liver disease such as obesity, diabetes, significant alcohol use, or a family history of liver problems. AST may also be tested on a panel like the comprehensive metabolic panel during routine health checkups.
• Diagnosis takes place after symptoms have occurred and is the process of finding the cause of those symptoms. For example, AST may be measured if you have had jaundice, fatigue, swelling, unexplained weight loss, itching, nausea, and vomiting, or other symptoms that are associated with liver problems.
• Monitoring describes the steps that are taken to see how your health situation evolves. In some cases, you may have repeated tests that include AST at frequent intervals in order to track your liver health. AST can be measured to help determine how well treatment for liver problems is working. A panel test with AST can also check for signs of liver damage if you start taking a medication that could potentially affect your liver.

What does the test measure?

An AST test measures the level of aspartate aminotransferase in your blood. AST is an enzyme that is normally present in the liver, heart, brain, pancreas, kidneys, and many other muscles and tissues in the body. Enzymes like AST help facilitate fundamental biological processes in these organs and tissues.

It is common for AST to be measured as part of a panel of other enzymes and proteins in the blood because it may provide your doctor with a better view of your overall condition compared to only evaluating the AST test result.

When should I get an aspartate aminotransferase test?

A measurement of AST in your blood may be beneficial in several different medical situations. If you have symptoms of liver disease, a panel test that includes AST can help assess the cause and determine the severity of the problem.

Tests that measure AST like the liver panel and comprehensive metabolic panel are often used as diagnostic tests if you have to go to the emergency room or if you have general symptoms that could be caused by many types of health problems.

Testing your levels of AST can be appropriate as a form of screening, especially if you are at high risk of liver problems. Some doctors prescribe AST testing during normal check-ups even for people without risk factors for liver disease. Despite this, there is no clear medical evidence showing that this broad approach to screening generates more benefits than drawbacks, which can include increased costs and unnecessary follow-up tests.

An AST test may be utilized for monitoring if you have previously had an abnormal test result or a diagnosed liver disease. If you begin taking a new medication that can affect the liver, your doctor may prescribe a lipid panel with an AST measurement to monitor for possible side effects.

How to get tested

Tests for AST are usually prescribed by a doctor and conducted in a doctor’s office, hospital, or laboratory where blood is drawn from a vein in your arm. Results are determined through laboratory analysis of your blood sample.