What Is a GGT Test?

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.

What Do High Levels of GGT Mean?

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.

How Is a GGT Test Done?

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.

WebMD Medical Reference Reviewed by Melinda Ratini, DO, MS on June 23, 2019

Sources

SOURCES:

Mayo Clinic: “Viral gastroenteritis,” “Inflammatory bowel disease,” “Liver disease.”

American Cancer Society: “Signs and Symptoms of Stomach Cancer.”

Lab Tests Online: “Gamma-Glutamyl Transpeptidase (GGT).”

Clinical Reviews in Clinical Laboratory Sciences: “Gamma Glutamyl Transferase.”

University of Rochester Medical Center: “Gamma-Glutamyl Transpeptidase.”

Disease Markers: “Gamma-Glutamyltransferase: A Predictive Biomarker of Cellular Antioxidant Inadequacy and Disease Risk.”

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