Gamma-glutamyl Transferase (GGT) Test
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A gamma-glutamyl transferase (GGT) test measures the amount of GGT in your blood GGT is an enzyme. Enzymes are proteins that speed up certain chemical reactions in your body. Thousands of enzymes play an important role in all of your body functions.
The GGT enzyme is found throughout your body, but it is mainly found in your liver. If your liver or bile duct is damaged, GGT may leak into your bloodstream. So high levels of GGT in your blood may be a sign of liver disease or damage to the bile ducts.
Bile ducts are tubes that carry bile in and out of the liver. Bile is a fluid made by the liver that is important for digestion. A GGT test can't diagnose the specific cause of liver disease.
The test can only indicate that your liver is being damaged. This test is usually done with or after other liver function tests, most often an alkaline phosphatase (ALP) test. ALP is another type of liver enzyme.
While both your GGT and ALP may be elevated in diseases that affect your bile ducts and liver, only ALP will be elevated in bone disease. This helps your health care provider to understand if your issue may be due to a bone disorder instead of your liver.
Why this test is done
You may need a GGT test if you have symptoms of liver disease. They may include:
- Fatigue
- Weakness
- Jaundice, a condition that causes your skin and eyes to turn yellow
- Loss of appetite
- Abdominal (belly) pain or swelling
- Nausea and vomiting
- Severe itching
Your provider may use this test to monitor your alcohol use if you're being treated for AUD. You may also need this test if you have abnormal results on an ALP test and/or other liver function tests.
How to prepare
Talk to your provider to see if there are any specific instructions, since. the results of your GGT test may be affected by:
- Certain medicines or supplements
- Drinking alcohol
- Smoking cigarettes
GGT levels go down after meals. Your provider may also ask you to fast for a certain amount of time before testing.
Sample type
Blood
Other names for this test
gamma-glutamyl transpeptidase, GGTP, Gamma-GT, GTP
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Educational content only. This entry describes what a test measures and how published reference ranges are defined. It is not a diagnosis, does not interpret your personal results, and is not a substitute for a qualified doctor.