Gamma-glutamyl Transferase

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

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

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 After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.

Generally, no preparation is required for this test.

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

Abnormal levels of GGT can be found in the following conditions:

• 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.