Alanine transaminase (ALT) blood test

Definition

The alanine transaminase (ALT) blood test measures the level of the enzyme ALT in the blood.

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

No special preparation is needed.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

ALT is an enzyme found in a high level in the liver. An enzyme is a protein that causes a specific chemical change in the body.

Injury to the liver results in release of ALT into the blood.

This test is mainly done along with other tests (such as AST, ALP, and bilirubin) to diagnose and monitor liver disease.

Normal Results

The normal range is 4 to 36 U/L.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your health care provider about the meaning of your specific test results.

What Abnormal Results Mean

An increased ALT level is often a sign of liver disease. Liver disease is even more likely when the levels of substances checked by other liver blood tests have also increased.

An increased ALT level may be due to any of the following:

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:


Review Date: 1/26/2019
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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