Alanine aminotransferase (alt) test

An alanine aminotransferase (ALT) test measures the amount of the enzyme ALT in the blood. ALT is found mainly in the liver. When ALT levels are higher than normal, it can mean that the liver is damaged or diseased.

The ALT test is done to:

• Look for liver disease, such as hepatitis.
• Help check for liver damage.
• Find out whether jaundice was caused by a blood disorder or liver disease.
• Keep track of the effects of medicines that can damage the liver.

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

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

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.

High values

High levels of ALT may be caused by:

• Liver damage from conditions such as hepatitis or cirrhosis.
• A heart attack.
• Very strenuous exercise or severe injury to a muscle.
• Taking too much of a medicine, such as acetaminophen.
• Mononucleosis.
• Some genetic conditions, such as Wilson's disease.