AST (SGOT)

What is AST (SGOT)?

AST, short for aspartate aminotransferase and formerly known as SGOT, is an enzyme involved in the conversion of amino acids. It also plays a role in the chemical reactions through which cells produce energy. It is found mostly in the liver; it is also present in heart muscle, skeletal muscles, the kidneys, the brain and red blood cells. AST is normally present in the blood at low levels; when cells in these tissues are damaged, it is released into the blood and its level rises.

Because AST is found in many different tissues, it is not an enzyme specific to the liver. It is therefore usually ordered together with ALT, which is more specific to the liver, and the ratio of the two enzymes to each other can also guide doctors. The test is run on the serum portion of blood drawn from the arm, using kinetic methods that measure the enzyme's reaction rate. The result is more meaningful when evaluated together with the other tests in the liver panel, such as ALP, GGT and bilirubin.

When is an AST test ordered?

AST is frequently ordered in routine health check-ups as part of the panel known as liver function tests. Because liver diseases may cause no symptoms for a long time, it is used for screening in people at risk. In people being treated with medications that can affect the liver and in those with a known liver disease, it is repeated at regular intervals to monitor the course. When a muscle disease is suspected, it is also evaluated together with the muscle enzyme CK.

• Yellowing of the skin or the whites of the eyes, dark urine or pale stools
• Pain in the upper right abdomen, nausea, loss of appetite and unexplained fatigue
• Regular alcohol use, fatty liver or suspected exposure to a hepatitis virus
• Regular monitoring during treatment with medications that can affect the liver
• Investigation of muscle diseases that cause muscle pain and weakness

How do I prepare for an AST test?

You usually do not need to fast for an AST test; however, if it has been ordered together with other tests in the liver panel, you may be advised to give blood in the morning on an empty stomach. Because heavy exercise can increase the release of AST from muscle cells into the blood, avoiding intense exercise and alcohol for a day or two before the test makes the result more reliable.

Many substances, such as painkillers, some antibiotics, cholesterol medications and herbal products, can affect liver enzymes. Share a list of the medications, vitamins and herbal supplements you take with your doctor; do not stop a prescribed medication without consulting your doctor. Taking the sample takes a few minutes and can be done at your home or workplace at your appointment time.

What does an AST result mean?

High AST mostly suggests damage to liver cells; fatty liver, viral hepatitis, alcohol-related liver disease, medication side effects and cirrhosis are among the main causes. Outside the liver, intense exercise, muscle injuries, muscle diseases, heart muscle damage and the destruction of red blood cells can also raise the value. An AST level that is markedly higher than the ALT level can give the doctor a clue, particularly regarding alcohol-related liver damage or advanced liver disease.

Mild elevations are quite common and sometimes temporary; your doctor may therefore repeat the test after a while or order additional tests. Whether the values return to normal within a few weeks can also be helpful for the diagnosis. Low AST values, on the other hand, usually do not indicate a clinical problem. The normal limits for AST can vary with age, sex and the method used by the laboratory; on this page you can find the range of the laboratory that analyzes your sample. What the result means should be decided by your doctor, who considers your symptoms and your other liver tests together.