Alanine Aminotransferase (ALT) Test

Test Overview

An alanine aminotransferase (ALT) test measures the amount of this enzyme in the blood. ALT is found mainly in the liver, but also in smaller amounts in the kidneys, heart, muscles, and pancreas. ALT was formerly called serum glutamic pyruvic transaminase (SGPT).

ALT is measured to see if the liver is damaged or diseased. Low levels of ALT are normally found in the blood. But when the liver is damaged or diseased, it releases ALT into the bloodstream, which makes ALT levels go up. Most increases in ALT levels are caused by liver damage.

The ALT test is often done along with other tests that check for liver damage, including aspartate aminotransferase (AST), alkaline phosphatase, lactate dehydrogenase (LDH), and bilirubin. Both ALT and AST levels are reliable tests for liver damage.

Why It Is Done

The ALT test is done to:

• Identify liver disease, such as cirrhosis and hepatitis, caused by alcohol, drugs, or viruses.
• 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.

How To Prepare

In general, there is 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.

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.