Gamma-Glutamyl Transferase (GGT)
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- Also Known As:
- GGT
- Gamma-Glutamyl Transpeptidase
- GGTP
- Gamma-GT
- GTP

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At a Glance
Why Get Tested?
To evaluate for a possible liver disease or bile duct disease or to differentiate between liver and bone disease as a cause of elevated alkaline phosphatase (ALP); sometimes to screen for or monitor alcohol abuse
When To Get Tested?
When you have symptoms of a liver or bile duct disorder or as follow up when you have an increased ALP level
Sample Required?
A blood sample drawn from a vein
Test Preparation Needed?
GGT levels fall after meals; you may be instructed to fast (nothing to eat or drink except water) for at least 8 hours prior to the test. You may also be asked to stop drinking alcohol or taking certain prescription medications.
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What is being tested?
Gamma-glutamyl transferase (GGT) is an enzyme that is found in many organs throughout the body, with the highest concentrations found in the liver. GGT is elevated in the blood in most diseases that cause damage to the liver or bile ducts. This test measures the level of GGT in a blood sample.
Normally, GGT is present in low levels, but when the liver is injured, the GGT level can rise. GGT is usually the first liver enzyme to rise in the blood when any of the bile ducts that carry bile from the liver to the intestines become obstructed, for example, by tumors or stones. This makes it the most sensitive liver enzyme test for detecting bile duct problems.
However, the GGT test is not very specific and is not useful in differentiating between various causes of liver damage because it can be elevated with many types of liver diseases, such as liver cancer and viral hepatitis, as well as other non-hepatic conditions, such as acute coronary syndrome. For this reason, the GGT test is not recommended for routine use by itself. However, it can be useful in conjunction with other tests and in determining the cause of a high alkaline phosphatase (ALP) level, another enzyme found in the liver.
Both GGT and ALP are increased in liver diseases, but only ALP will be increased with diseases affecting bone tissue. Therefore, GGT can be used as a follow up to an elevated ALP to help determine if the high ALP result is due to liver or bone disease.
GGT levels are sometimes increased with consumption of even small amounts of alcohol. Higher levels are found more commonly in chronic heavy drinkers than in people who consume less than 2 to 3 drinks per day or who only drink heavily on occasion (binge drinkers). The GGT test may be used in evaluating someone for acute or chronic alcohol abuse.
Common Questions
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Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.
The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.
If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.
Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.
While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”
For more information, please read the article Reference Ranges and What They Mean.
Health Professionals – LOINC
LOINC Observation Identifiers Names and Codes (LOINC®) is the international standard for identifying health measurements, observations, and documents. It provides a common language to unambiguously identify things you can measure or observe that enables the exchange and aggregation of clinical results for care delivery, outcomes management, and research. Learn More.
Listed in the table below are the LOINC with links to the LOINC detail pages. Please note when you click on the hyperlinked code, you are leaving Testing.com and accessing Loinc.org.
LOINC | LOINC Display Name |
---|---|
2324-2 | Gamma glutamyl transferase [Catalytic activity/Vol] |
96593-9 | Gamma glutamyl transferase (DBS) [Catalytic activity/Vol] |
View Sources
Sources Used in Current Review
2019 review performed by Balu K Chacko, PhD, NRCC, University of Alabama at Birmingham.
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Gerald Koenig and Stephanie Seneff. Gamma-Glutamyltransferase: A Predictive Biomarker of Cellular Antioxidant Inadequacy and Disease Risk. Dis Markers. 2015; 2015: 818570. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4620378/. Accessed July 2019.
Low Gamma-GT Familial Intrahepatic Cholestasis. Rare Disease Database (National Organization for Rare Diseases, NORD). Available online at https://rarediseases.org/rare-diseases/low-gamma-gt-familial-intrahepatic-cholestasis/. Accessed July 2019.
Katarzyna Kowalska, Milena Ściskalska, Anna Bizoń, Mariola Śliwińska-Mossoń, Halina Milnerowicz. Influence of oral contraceptives on lipid profile and paraoxonase and commonly hepatic enzymes activities. J Clin Lab Anal. 2018 Jan; 32(1): e22194. Published online 2017 Mar 9. doi: 10.1002/jcla.22194. Accessed July 2019.
Falaq Naz, Smita Jyoti, Rahul, Nishat Akhtar, Yasir Hasan Siddique. Effect of Oral Contraceptive Pills on the Blood Serum Enzymes and DNA Damage in Lymphocytes Among Users. Ind J Clin Biochem (July-Sept 2016) 31(3):294–301. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4910851/. 11. Accessed July 2019.
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Jenny HDA, et al. The association of alcohol intake with gamma-glutamyl transferase (GGT) levels: evidence for correlated genetic effects. Drug Alcohol Depend. 2014 Jan 1; 134: 99–105. Published online 2013 Sep 27. doi: 10.1016/j.drugalcdep.2013.09.016. Accessed November 2019.
Sources Used in Previous Reviews
Mayo 2001 Test Catalog, Mayo Medical Laboratories, Rochester, MN, 2000 Mayo Press.
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British Liver Trust Information Service (Last update September, 10 2001). Cirrhosis. British Liver Trust. Available online at http://www.britishlivertrust.org.uk/publications/cirrhosis.html.
MEDLINEplus (October 3, 2001). Medical Encyclopedia: ESR. U.S. National Library of Medicine, Bethesda, MD. MEdlinePlus. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003638.htm.
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Carey, W (January 1, 2009). Approach to the Patient with Liver Disease: A Guide to Commonly Used Liver Tests, Cleveland Clinic. Available online at http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/hepatology/guide-to-common-liver-tests/. Accessed September 2009.
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