Gamma-glutamyl transpeptidase (GGT) is a test to measure the amount of the enzyme GGT in the blood.
How the Test is Performed
A blood sample is taken from a vein. This is called a venipuncture.
How to Prepare for the Test
The health care provider may tell you to stop taking any drugs that can affect the test.
Drugs that can increase GGT levels include:
Drugs that can decrease GGT levels include:
- Birth control pills
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
The normal range is 0 to 51 international units per liter (IU/L).
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What Abnormal Results Mean
Greater-than-normal levels of GGT may be due to:
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Bleeding from where the needle was inserted
- Fainting or feeling light-headed
- Hematoma (blood collecting under the skin)
- Infection (rare)
Gamma-GT; GGTP; GGT
Berk P, Korenblat K. Approach to the patient with jaundice or abnormal liver tests. In: Goldman L, Schafer AI, eds.Cecil Medicine
Pratt DS. Liver chemistry and function tests. In: Feldman M, Friedman LS, Brandt LJ, eds.Sleisenger and Fordtran's Gastrointestinal and Liver Disease
Update Date 1/21/2013
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.