Aspartate transaminase (AST) is an enzyme important in the metabolism of amino acids. It’s produced primarily by the liver, but is found in most tissues and especially in the heart, brain, and skeletal muscles. A test for serum (blood) AST is important in medical diagnosis, especially in conjunction with other enzyme blood tests. In particular, a test for alanine transaminase (ALT) in conjunction with AST can reveal the presence of liver disease, cardiovascular disease, and diseases of the skeletal muscles, as well as other conditions both benign and pathological.

Normal levels of AST are 6-34 IU/liter in women and 8-40 IU/liter in men.


When a blood test measures high AST, a wide range of possible causes exists. For that reason, it’s necessary to conduct other diagnostic tests in order to narrow down the possible causes of the elevation in AST levels in the blood.

High AST can be caused by liver diseases, myocardial infarction (heart attack), acute pancreatitis, acute hemolytic anemia, trauma (especially severe burns), acute kidney failure, diseases of the muscular and skeletal systems, and other causes. Sometimes the cause of the high AST result is obvious, e.g. if acute physical trauma is present. Many of the causes are asymptomatic, however, such as liver diseases. Unless the cause is obvious, more diagnostic work is called for.

Liver Disease

AST elevation can indicate liver disease, but because of the wide range of conditions that can cause the elevation it isn’t a good specific marker for liver disease. When AST is elevated but ALT is normal, this shows that the AST elevation is almost certainly caused by something other than an affliction of the liver.

When both the enzymes are elevated, a comparison of the two can provide information about the specific liver disease and its causes. When AST is elevated more than ALT, this commonly shows that the cause of the liver condition is alcohol-related. If ALT is elevated more than AST, this shows the presence of liver disease but suggests a non-alcoholic cause for the affliction. Alcohol abuse is the single most common cause of liver disease. Causes of liver disease other than alcohol abuse include obesity, type 2 diabetes, hereditary factors, side effects of medications, and viral and bacterial infections.

Further Diagnostic Tests

Depending on the specific outcome of the enzyme tests, other diagnostic procedures may be called for. Medical imaging is a useful diagnostic tool. If the tests indicate liver disease, an examination of the liver using ultrasound or computerized tomography (CT) scanning can show the presence of fatty deposits (fatty liver disease), fibrotic scarring (fibrosis), advanced scarring of the liver (cirrhosis), inflammation and
(hepatitis), or anomalous masses that may indicate either cancer of the liver or a non-cancerous tumor. A liver biopsy can confirm or eliminate the presence of cancer and also be used to test for viral and bacterial infections.

If the blood work indicates another cause for the elevated AST levels than liver disease, tests for heart problems, kidney functioning, and other diagnostic procedures related to the various non-liver causes of high AST are indicated.


Treatment for conditions causing elevated AST will depend, of course, on what the condition is. Recommendations can range from lifestyle changes (diet, weight loss, cessation of drinking, exercise, changes in prescription medications) to hospitalization and emergency trauma treatment or care for a heart attack or acute kidney failure.

Although elevated AST can indicate severe and potentially life-threatening conditions, by itself it is not a cause for alarm.

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