Definition of ALT:

Alanine transaminase (ALT) is an enzyme found in the highest amounts in the liver. Injury to the liver results in release of the substance into the blood.

This article discusses the test to measure the amount of ALT in the blood.

How the test is performed:

A blood sample is needed. For information on how this is done, see: Venipuncture

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

This test is used to determine if a patient has liver damage.

Normal Values:

Normal range can vary according to a number of factors, including age and gender. Normal value ranges may also vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean:

Increased levels of ALT often means that liver disease is present. Liver disease is even more likely when levels of other liver blood tests are also increased.

An increase in ALT levels may be due to:

• Cirrhosis (scarring of the liver)
• Death of liver tissue (liver necrosis)
• Hepatitis
• Hemochromatosis
• Lack of blood flow to the liver (liver ischemia)
• Liver tumor or cancer
• Medications that are toxic to the liver
• Mononucleosis ("mono")
• Pancreatitis (swollen and inflamed pancreas)

What the risks are:

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient 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:

• Bleeding from where the needle was inserted
• Fainting or feeling light-headed
• Hematoma (blood collecting under the skin)
• Infection (rare)