aspartate aminotransferase (ast) test

test overview

an aspartate aminotransferase (ast) test measures the amount of this enzyme in the blood. ast is normally found in red blood cells, liver, heart, muscle tissue, pancreas, and kidneys. ast formerly was called serum glutamic oxaloacetic transaminase (sgot).

low levels of ast are normally found in the blood. when body tissue or an organ such as the heart or liver is diseased or damaged, additional ast is released into the bloodstream. the amount of ast in the blood is directly related to the extent of the tissue damage. after severe damage, ast levels rise in 6 to 10 hours and remain high for about 4 days.

the ast test may be done at the same time as a test for alanine aminotransferase, or alt. the ratio of ast to alt sometimes can help determine whether the liver or another organ has been damaged. both alt and ast levels can test for liver damage.

why it is done

this test is done to:

• check for liver damage.
• help look for liver disease, such as hepatitis. liver disease may cause symptoms. these may include pain in the upper belly, nausea, vomiting, and sometimes jaundice.
• check to see how well treatment for liver disease is working.
• find out if jaundice was caused by a blood disorder or liver disease.
• keep track of the effects of cholesterol-lowering medicines and other medicines that can damage the liver.

how to prepare

in general, there's nothing you have to do before this test, unless your doctor tells you to.

how it is done

a health professional uses a needle to take a blood sample, usually from the arm.

how long the test takes

the test will take a few minutes.

watch

how it feels

when a blood sample is taken, you may feel nothing at all from the needle. or you might feel a quick sting or pinch.

risks

there is very little chance of having a problem from this test. when a blood sample is taken, a small bruise may form at the site.

results

each lab has a different range for what's normal. your lab report should show the range that your lab uses for each test. the normal range is just a guide. your doctor will also look at your results based on your age, health, and other factors. a value that isn't in the normal range may still be normal for you.

results are usually available within 12 hours.

high values

high levels of ast may be caused by:

• liver damage from conditions such as hepatitis or cirrhosis.
• a heart attack or heart failure.
• many medicines, such as statins, antibiotics, chemotherapy, aspirin, opioids, and barbiturates.
• very strenuous exercise or severe injury to a muscle.
• high doses of vitamin a.
• kidney or lung damage.
• mononucleosis.
• some types of cancer.