A GGT (gamma-glutamyl transferase) test measures the levels of GGT in the blood.
GGT is an enzyme mainly found in the liver but also throughout the body. When the liver is damaged, GGT levels can go to the bloodstream. Thus, high levels of GGT in the blood may be a sign of liver damage or disease. The GGT levels can also increase due to medications or alcohol.
GGT is typically the first liver enzyme to increase in the blood when the liver bile ducts become blocked or constricted. GGT is the most sensitive liver enzyme test for finding bile duct issues.
A GGT test alone can't diagnose the specific cause of liver disease. It is usually requested with or after other liver function tests, such as the alkaline phosphatase (ALP) blood test.
A doctor may order a GGT test for the following reasons:
This is a single-marker test measuring GGT. It can be ordered as part of a custom panel. GGT is used in the diagnosis and monitoring of hepatobiliary diseases.