ALT, or alanine aminotransferase, is one of the two liver enzymes. It is sometimes known as serum glutamic-pyruvic transaminase, or SGPT. It is a protein made only by liver cells. When liver cells are damaged, ALT leaks out into the bloodstream and the level of ALT in the blood is elevated.

Scroll over image to see an animation of liver enzymes leaking into the blood.

Explanation of test results:

A high ALT level often means there is some liver damage, but it may not be related to hepatitis C. It is important to realize the ALT level goes up and down in most patients with hepatitis C. The ALT level does not tell you how much liver damage there is, and small changes are common. Changes in the ALT level do not mean the liver is doing any better or any worse. The ALT level does not indicate how much scarring (fibrosis) is in the liver and it does not predict how much liver damage will develop. A normal ALT does not mean the hepatitis C is cured.

Other things to know:

• Many patients with hepatitis C will have a normal ALT level.
• Patients can have very severe liver disease and cirrhosis and still have a normal ALT level.
• When a patient takes treatment for hepatitis C, it is helpful to see if the ALT level goes down.