Gamma-Glutamyl Transpeptidase

Does this test have other names?

GGTP, gamma-glutamyl transferase, GGT, Gamma-GT, GTP 

What is this test?

This test checks the level of the enzyme gamma-glutamyl transpeptidase (GGT) in your blood.

GGT is found in many organs, with the highest levels in liver cells. This test helps your healthcare provider look for possible damage to your liver or problems with the liver ducts or gallbladder. It can also help tell the difference between liver and bone disease if your results from a different blood test called alkaline phosphatase are abnormal.

Why do I need this test?

You may need this test if you have other abnormal liver blood tests or your healthcare provider suspects that you have liver damage. One symptom of liver damage is jaundice, a yellowish tint to your skin and eyes. You may also need this test to see if you have liver or bone disease. This test is also used to look for chronic alcohol abuse.

What other tests might I have along with this test?

Your healthcare provider may also order other liver enzyme tests. These include:

• Alanine aminotransferase, or ALT

• Alkaline phosphatase, or ALP

• Aspartate aminotransferase, or AST 

• 5'-Nucleotidase

• Creatine phosphokinase, or CPK

• Lactic dehydrogenase, or LDH

• Leucine aminopeptidase, or LAP 

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

Results are given in international units per liter (IU/L). Normal findings are:

• 0 to 30 IU/L for adults

Normal results for children are much like those for adults. A newborn's level is 6 to 7 times higher than an adult's.

Higher than normal test results could be a sign of liver damage from diseases, such as hepatitis, cirrhosis, tumors, or pancreatic cancer. But a higher than normal GGT level does not tell you the specific cause of liver disease or damage.

GGT may be higher with diabetes, congestive heart failure, or pancreatitisis.

Higher GGT levels also may mean liver damage from heavy, chronic alcohol abuse. GGT levels that are higher than normal may also signal a viral infection, such as Epstein-Barr.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Your test results might be affected if you are near the end of your pregnancy. Phenobarbital, phenytoin, and other medicines can increase your GGT levels. Other medicines such as clofibrate and birth control pills can lower your levels.

How do I get ready for this test?

You may be asked to not eat or drink anything but water for 8 hours before having this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.