Gamma-Glutamyl Transferase (GGT) Test: What It Is & Results

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A gamma-glutamyl transferase (GGT) test is a blood test providers use to diagnose or rule out liver and bile duct conditions. It measures levels of GGT, an enzyme found mostly in your liver that helps protect your cells from damage. Alcohol, medications and conditions that affect your liver, pancreas or heart can cause high GGT levels.

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Gamma-glutamyl transferase (GGT) is an enzyme (something that helps chemical reactions happen) found mainly in your liver, though it can be found throughout your body. It helps protect your cells from damage — so, high levels of it can mean it’s working hard against damage in your body.

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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

A gamma-glutamyl transferase (GGT) test is a blood test a healthcare provider orders to check for liver damage or a bile duct blockage. It measures the amount of GGT, a liver enzyme, in your blood.

High levels of GGT can indicate a number of health conditions that affect your liver, your heart or other organs. Alcohol and certain medications can also cause high levels of GGT. Healthcare providers can’t use GGT levels alone to diagnose a disease. They usually order a GGT blood test with other liver function tests to help reach a diagnosis.

Other names for a gamma-glutamyl transferase include:

• Gamma-glutamyl transpeptidase.
• GGTP.
• Gamma-GT.
• GTP.

Healthcare providers most often use GGT blood tests to help diagnose liver disease and/or liver bile duct issues. Your provider may have you get a GGT blood test if you:

• Have signs and symptoms of liver disease or bile duct obstructions. Providers often order a GGT blood test alongside other tests, such as alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and bilirubin tests, to diagnose liver and bile duct issues.
• Have elevated alkaline phosphatase (ALP) levels. GGT levels can give your provider more information to help diagnose the cause of high ALP levels. For instance, liver or bile duct issues can cause elevated levels of both GGT and ALP. Bone issues cause high ALP but don’t usually affect GGT.
• Are at risk for or in treatment for alcohol use disorder. Healthcare providers can use a GGT test to screen for alcohol use disorder. If you’re receiving treatment for alcohol use disorder or alcoholic hepatitis, your provider can use a GGT test to help manage your treatment.

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Before a GGT blood test:

• Your healthcare provider may have you temporarily stop taking certain medications. Only stop if your provider tells you to.
• Tell your provider about any drugs or dietary supplements you’re taking. Many different types of medications and supplements can affect your GGT levels.
• Don’t consume any alcohol for at least 24 hours before the test. Even small amounts of alcohol can increase your GGT levels.

Your provider will need to send a sample of your blood to a lab for a GGT test. To get a sample:

• You’ll sit in a chair, and a provider will check your arms for an easily accessible vein. This is usually in the inner part of your arm on the other side of your elbow.
• They’ll clean and disinfect the area.
• They’ll insert a small needle into your vein to take a blood sample. This may feel like a pinch.
• A small amount of blood will collect in a test tube.
• The provider will remove the needle and hold a cotton ball or gauze on your skin to stop the bleeding and cover it with a bandage.

The entire procedure usually takes less than five minutes.

After a healthcare provider has collected your blood sample, they’ll send it to a lab for testing. Your healthcare provider will review your results and share them with you, or they’ll appear in your electronic health record.

Blood tests come with a small risk of infection. You may also have a bruise where your provider inserted the needle.

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The normal range for GGT is often below 50 U/L (unit per liter), but it can vary based on the lab that performs the test. Always check the reference range provided on your results. It will show a typical, or usual range for the results.

It’s important to note that GGT levels are, on average, somewhat higher in males. They can also vary with age.

In most cases, you should have your test results within one to two business days, though it could take longer.

Having higher-than-normal GGT levels in your blood may indicate that a condition or disease is damaging your liver. But GGT levels alone can’t identify the specific cause of the damage.

Liver conditions that can cause elevated GGT levels include:

• Hepatitis (liver inflammation), especially viral hepatitis and alcoholic hepatitis.
• Cirrhosis.
• Cholestasis (blocked liver bile duct).
• Alcohol liver disease.
• Non-alcohol related steatotic (fatty) liver disease.
• Liver ischemia (not enough blood flow to your liver, which leads to death of liver tissue).
• A liver tumor or liver cancer.

Other conditions that can cause elevated GGT levels include:

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• Alcohol use disorder.
• Pancreatitis or pancreatic cancer.
• Diabetes.
• Congestive heart failure.
• Certain medications (like phenobarbital, phenytoin or warfarin).
• Consuming alcohol before your blood draw.
• Smoking.

It’s important to know that having a high GGT test result doesn’t necessarily mean you have a medical condition. Other factors can affect your GGT levels. Your healthcare provider will take your other blood test results and your medical history into consideration when analyzing your results.

Talk to your provider if you have any questions about why you need a GGT test or what the results mean.

Seeing a test result that’s not as expected can be stressful. The thing about GGT levels is that they don’t indicate any specific disease on their own, so an internet search may not be able to give you quick answers about what your results mean for you. Your provider will use your other test results, any symptoms you’re experiencing and your health history to come to a diagnosis. They can help you understand what your specific results mean for your health.

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Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

• Kunutsor SK. Gamma-glutamyltransferase-friend or foe within? (https://pubmed.ncbi.nlm.nih.gov/27512925/) Liver Int. 2016 Dec;36(12):1723-1734. Accessed 10/21/2024.
• National Library of Medicine (U.S.). Gamma-glutamyl Transferase (GGT) Test (https://medlineplus.gov/lab-tests/gamma-glutamyl-transferase-ggt-test/). Updated 11/16/2021. Accessed 10/21/2024.
• Xing M, Gao M, Li J, Han P, Mei L, Zhao L. Characteristics of peripheral blood Gamma-glutamyl transferase in different liver diseases (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8735790/). Medicine (Baltimore). 2022 Jan 7;101(1):e28443. Accessed 10/21/2024.

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