An AST blood test is usually requested alongside several other tests to help evaluate a patient who has symptoms of a liver disorder. Some of these symptoms include jaundice (yellowing of the eyes and skin), dark urine, nausea, vomiting, abdominal swelling, unusual weight gain, and abdominal pain. AST can also be requested, either by itself or with other tests, for:
persons who might have been exposed to hepatitis viruses,
persons taking drugs that can occasionally damage the liver.
Individuals who have mild symptoms, such as tiredness, may have AST measured to make sure they do not have long-term (chronic) liver disease. AST is often measured to monitor treatment of persons with liver disease, and may be requested either in isolation or alongside other tests.
Very high concentrations of AST (more than 10 times the upper limit of normal (ULN)) are usually due to a rapidly developing liver disease called acute hepatitis, which is often caused by a virus infection. In acute hepatitis, AST concentrations usually stay elevated for about 1–2 months, but can take as long as 3–6 months to return to normal. In the slowly developing variety of liver disease, chronic hepatitis, AST results are usually not as high, often less than 4 times the upper limit of normal (ULN). In chronic hepatitis, AST often varies between normal and slightly increased, so doctors might request the test regularly to determine the pattern of change.
In some diseases of the liver, especially when the bile ducts are totally or partially blocked, or with cirrhosis and certain cancers of the liver, AST concentrations may be close to normal. When liver damage is due to alcohol, AST often increases much more than ALT (this is a pattern seen with few other liver diseases). The concentration of AST can also be increased following the breakdown of red blood cells (haemolysis) after a heart attack and as a result of muscle injury.
An injection of medicine into muscle tissue, or even strenuous exercise, may increase AST concentrations within the bloodstream. In rare instances, some drugs can damage the liver or muscle, increasing AST concentrations. This is true of both prescription drugs and some 'natural' or herbal health products. If your doctor finds that you have high levels of AST, tell him or her about all the drugs and health products you are taking.
This article was last reviewed on 31 August 2012. | This article was last modified on 22 March 2016.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.