What Is a GGT Test?

Medically Reviewed by Gabriela Pichardo, MD on June 12, 2021
2 min read

Health conditions like inflammatory bowel disease, stomach cancer, or liver disease can cause many of the same symptoms -- stomach pain, fatigue, and a lack of appetite. If you have these, your doctor probably will recommend a few tests to figure out what's going on, and that might include a GGT test.

GGT stands for gamma-glutamyl transpeptidase or gamma-glutamyl transferase. It’s a common enzyme found in many of your body’s tissues and organs, including your liver. It also turns up in your blood and other bodily fluids.

Experts don't really understand the role GGT plays, but it seems to have something to do with breaking down, changing, and moving proteins and other molecules in your body.

Your results will be in international units per liter, or IU/L. In adults, GGT levels in the range of 0 to 30 IU/L are normal. Anything above 30 IU/L could be a sign that your liver isn’t working the way it should. Several types of liver disease can cause a rise in GGT, including:

But high GGT levels alone aren’t enough for your doctor to know if you have liver disease. For example, doctors often also recommend other tests, including one related to alkaline phosphatase (ALP), another enzyme that can build up in your blood if your liver isn’t working well.

A GGT test can also help doctors diagnose or manage several other medical issues:

Other conditions that can raise your GGT level include congestive heart failure and diabetes.

It’s a blood test, so a nurse will take a sample of your blood from a vein in your arm. Your doctor may ask you not to eat or drink anything for 8 hours before the test.

Some medications, like the anti-seizure drugs phenytoin and phenobarbital, can raise your GGT levels. Before a GGT test, tell your doctor about any medications -- or supplements -- you take.