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Gamma-glutamyltransferase, abbreviated as GGT, is an enzyme that is found mainly in the liver. However, it is also found in the:

• kidneys
• biliary tract
• heart
• brain
• intestine
• pancreas
• spleen

Who is a candidate for the test?

GGT levels are measured when a healthcare professional suspects damage or disease in the liver or the biliary system.

How is the test performed?

In order to measure the amount of GGT in the blood, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a rubber tube called a tourniquet is tied around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them.

A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.

What is involved in preparation for the test?

Generally, no preparation is required for this test.

What do the test results mean?

For men, the normal range for GGT are 2 to 30 U/L. For women, the normal range is 1 to 24 U/L.

• alcoholism
• brain tumor
• diabetes
• gallbladder disease or other diseases of the biliary system
• heart attack
• liver diseases such as hepatitis, cirrhosis, or cancer
• mononucleosis
• pancreatitis

In addition, certain medicines that are used to prevent seizures such as carbamazepine (i.e., Carbatrol, Equetro, Tegretol), phenobarbital, and phenytoin (i.e., Dilantin) may cause GGT to rise to an abnormal level.