Gamma-glutamyltransferase is a transferase that catalyzes the transfer of gamma-glutamyl functional groups from molecules such as glutathione to an acceptor that may be any amino acid, a peptide or water.
This test is often done with other tests that measure liver enzymes if there’s a possibility of liver damage. Your doctor may order the GGT test if they suspect your liver is damaged or if you have liver disease, particularly if it’s related to alcohol use. The GGT test is currently the most sensitive enzymatic indicator of liver damage and disease. This damage is often caused by heavy use of alcohol or other toxic substances, like drugs or poisons.
Your doctor may instruct you to fast for eight hours before the test and to stop taking certain medications. If you drink even a small amount of alcohol within 24 hours of the test, it can affect your results. A regular blood test can measure your GGT level. Usually, blood is drawn from your arm at the crease of your elbow.
The normal range for GGT levels is 9–48 units per liter (U/L). Normal values can vary due to age and sex. The GGT test can diagnose liver damage, but it can’t determine the cause. If your GGT level is elevated, you’ll probably have to undergo more tests.