Patient Test Information

Gamma-Glutamyl Transferase (GGT)

  • 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.

  • 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.

  • How is the test used?

    The gamma-glutamyl transferase (GGT) test may be used to determine the cause of elevated alkaline phosphatase (ALP). Both ALP and GGT are elevated in disease of the bile ducts and in some liver diseases, but only ALP will be elevated in bone disease. Therefore, if the GGT level is normal in a person with a high ALP, the cause of the elevated ALP is most likely bone disease.

    The GGT test is sometimes used to help detect liver disease and bile duct obstructions. It is usually ordered in conjunction with or as follow up to other liver tests such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), ALP, and bilirubin. (Read also about the Liver Panel.) In general, an increased GGT level indicates that the liver is being damaged but does not specifically point to a condition that may be causing the injury.

    GGT can be used to screen for chronic alcohol abuse (it will be elevated in about 75% of chronic drinkers) and to monitor for alcohol use and/or abuse in people who are receiving treatment for alcoholism or alcoholic hepatitis.

    When is it ordered?

    A GGT test may be ordered when you have an elevated ALP level. An ALP test may be ordered alone or as part of a routine liver panel to screen for liver damage, even if no symptoms are present. A GGT test may be ordered when results of the ALP test are high but other tests that are part of the liver panel (such as AST and ALT) are not increased.

    GGT may be ordered along with or as a follow up to other liver function tests when you have signs or symptoms that suggest liver disease, such as:

    • Weakness, fatigue
    • Loss of appetite
    • Nausea and vomiting
    • Abdominal swelling and/or pain
    • Jaundice
    • Dark urine, light-colored stool
    • Itching (pruritus)

    GGT may also be ordered when someone with a history of alcohol abuse has completed alcohol treatment in order to monitor compliance with the treatment program.

    What does the test result mean?

    Results of the GGT are interpreted along with ALP results and with other tests results that may have been performed at the same time, such as a liver panel.

    An elevated ALP with a high GGT level helps rule out bone disease as the cause of the increased ALP level. An elevated ALP with a low or normal GGT means the increased ALP is more likely due to bone disease.

    An elevated GGT level suggests that a condition or disease is damaging the liver but does not indicate specifically the cause of the damage. In general, the higher the level, the greater the damage to the liver. Elevated levels may be due to liver diseases, such as hepatitis or cirrhosis, but they may also be due to other conditions, such as congestive heart failure, metabolic syndrome, diabetes, or pancreatitis. They may also be caused by alcohol abuse, alcoholic liver disease, or use of drugs that are toxic to the liver.

    A low or normal GGT test result indicates that it is unlikely that you have liver disease or have consumed any alcohol.

    Can my GGT level be elevated if I don't have any symptoms?

    Yes, GGT is very sensitive and can be increased when you don't have symptoms. This elevation may be temporary, perhaps due to medications that you are taking or due to drinking alcohol within 24 hours of the test. If other liver enzymes are normal, your healthcare practitioner may choose to repeat the GGT test at a later date. If the GGT is very high and/or your other liver enzymes are elevated, it may be necessary to have additional testing to identify the cause.

    I am an alcoholic, but I have quit drinking. Will my GGT ever go back to normal?

    Over time, your GGT level will fall from whatever level it was at when you stopped drinking alcohol to within the normal range. This can take several weeks to more than a month. Abstaining from alcohol will decrease your chances of further damaging your liver and should allow your liver function to improve.

    Is there anything else I should know?

    Even small amounts of alcohol within 24 hours of a GGT test may cause a temporary increase in the GGT. However, genetic variability between individuals can cause differences in this response of GGT to alcohol use. Smoking can also increase GGT.

    Elevated GGT levels may be an indicator of cardiovascular disease and/or hypertension. Some studies have shown that people with increased GGT levels have an elevated risk of dying from heart disease, but the reason for this association is not yet known.

    Low levels of GGT are observed in certain genetic diseases where the flow of bile from liver is interrupted or suppressed.

    Drugs that may cause an elevated GGT level include phenytoin, carbamazepine, and barbiturates such as phenobarbital. Use of many other prescription and non-prescription drugs, including nonsteroidal anti-inflammatory drugs (NSAIDs), lipid-lowering drugs, antibiotics, histamine receptor blockers (used to treat excess stomach acid production), antifungal agents, antidepressants, oral contraceptives and hormones such as testosterone, can increase GGT levels. Certain anticoagulants (e.g., heparin) and immunosuppressive medications (e.g., methotrexate) also increase GGT levels in serum.

    Levels of GGT increase with age in women, but not in men, and are always somewhat higher in men than in women.

  • View Sources

    Sources Used in Current Review

    2019 review performed by Balu K Chacko, PhD, NRCC, University of Alabama at Birmingham.

    (Updated December 11, 2013) Gamma-Glutamyltransferase. Medscape. Available online at Accessed July 2019.

    Diagnosis and Monitoring of Hepatic Injury. I. Performance Characteristics of Laboratory Tests. Dufour DR, Lott JA, Nolte FS, Gretch DR, Koff RS, Seeff LB. Clinical Chemistry 46:122027–2049 (2000). Available online at Accessed July 2019.

    Jenny H.D.A. van Beek, Marleen H.M. de Moor, Lot M. Geels, Michel R.T. Sinke, Eco. J.C. de Geus, Gitta H. Lubke, Cornelis Kluft, Jacoline Neuteboom, Jacqueline M. Vink, Gonneke Willemsen, and Dorret I. Boomsma. 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. Available online at Accessed July 2019.

    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 Accessed July 2019.

    Low Gamma-GT Familial Intrahepatic Cholestasis. Rare Disease Database (National Organization for Rare Diseases, NORD). Available online at 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 11. Accessed July 2019.

    Kazemi-Shirazi L1, Endler G, Winkler S, Schickbauer T, Wagner O, Marsik C. Gamma glutamyltransferase and long-term survival: is it just the liver? Clin Chem. 2007;53(5):940-6. Available online at Accessed July 2019.

    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.

    Worman, H (1998). Common Laboratory Tests in Liver Diseases. Columbia University Health Sciences. Available online at

    Johnston, D (April 15, 1999). Special Considerations in Interpreting Liver Function Tests. American Family Physician: American Academy of Family Physicians. Available online at

    Riley, T (November 1, 2001). Preventive Strategies in Chronic Liver Disease: Part I. Alcohol, Vaccines, Toxic Medications and Supplements, Diet and Exercise. American Family Physician: American Academy of Family Physicians. Available online at

    British Liver Trust Information Service (Last update September, 10 2001). Cirrhosis. British Liver Trust. Available online at

    MEDLINEplus (October 3, 2001). Medical Encyclopedia: ESR. U.S. National Library of Medicine, Bethesda, MD. MEdlinePlus. Available online at

    Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

    Pagana, Kathleen D. & Pagana, Timothy J. (1999). Mosby's Diagnostic and Laboratory Test Reference 4th Edition: Mosby, Inc., Saint Louis, MO.

    Dufour DR, et al. Diagnosis and monitoring of hepatic injury - I. Characteristics of laboratory tests. Clin Chem 2000; 46:2027-2049.

    Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006 Pg 613.

    Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006, Pp. 259-260.

    Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry. AACC Press, Washington, DC, Pg. 271.

    Carey, W (January 1, 2009). Approach to the Patient with Liver Disease: A Guide to Commonly Used Liver Tests, Cleveland Clinic. Available online at Accessed September 2009.

    Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson RA and Pincus MR, eds. Philadelphia: 2007, Pp 86, 275.

    (2000) Dufour, DR et al. National Academy of Clinical Biochemistry Standards of Laboratory Practice: Laboratory Guidelines for Screening, Diagnosis and Monitoring of Hepatic Injury. Available online at

    National Digestive Diseases Information Clearinghouse, part of NIDDK, NIH. NSAIDS and Peptic Ulcers. Available online at Accessed September 20, 2010.

    MedlinePlus Medical Encyclopedia: Gamma-glutamyl transpeptidase. Available online at Accessed September 20, 2010.

    Gamma-glutamyl transpeptidase. (Updated Jan. 21, 2013.) MedlinePlus Medical Encyclopedia. Available online at Accessed September 2013.

    Kim, KM et al. (Dec. 2012) Serum gamma-glutamyltransferase as a risk factor for general cardiovascular disease prediction in Koreans. National Center for Biotechnology Information PubMed database. Available online at Accessed September 2013.

    Gamma-glutamyltransferase level and risk of hypertension: a systematic review and meta-analysis. PLOS. Available online through at Accessed September 2013.

    Ghadban, R. et. al. (Updated Aug. 2, 2012). Gamma-Glutamyltransferase. Medscape. Available online at Accessed September 2013.

    KidsHealth. Blood Test: Gamma-Glutamyl Transpeptidase (GGT). Available online at Accessed September 2013.

    George, Hank. GGT - Gammaglutamyl Transferase. December, 2000. Available online at Accessed September 2013.

    General Practice Notebook. GGT and alcohol intake. Available online at Accessed September 2013.

    (Jan 2016) American Liver Foundation. Liver Function Tests. Available online at Accessed August 13, 2016.

    (Nov 2009) Gowda, S. et. al. A review on laboratory liver function tests. The Pan African Medical Journal. Available online at Accessed August 13, 2016.

    (May 2015) M. Lazo and J. Clark. Johns Hopkins Medicine POC-IT Guides. Liver function. Available online at Accessed August 13, 2016.

    (Feb 2015). MedlinePlus. Gamma-glutamyl transpeptidase (GGT) blood test. Available online at Accessed August 13, 2016.