Gamma-Glutamyl Transpeptidase

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

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

GGT is found in many organs. The highest levels are 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 blood test called alkaline phosphatase are abnormal.

You may need this test if you have other abnormal liver blood tests, or your healthcare provider thinks that you have liver damage. One symptom of liver damage is jaundice. This is 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.

You may have other liver enzyme tests. These include:

• Alanine aminotransferase

• Alkaline phosphatase

• Aspartate aminotransferase 

• 5'-Nucleotidase

• Creatine phosphokinase

• Lactic dehydrogenase

• Leucine aminopeptidase

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

Results are given in units per liter (U/L). In general, normal results are:

• 7 to 47 U/L for males

• 5 to 25 U/L for females

Normal results for children are like those for adults. A newborn's level is 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 cause of liver disease or damage.

GGT may be higher with diabetes, heart failure, hyperthyroidism, or pancreatitis.

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.

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

Having a blood test with a needle has 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. 

Phenobarbital, phenytoin, and other medicines can increase your GGT levels. Other medicines, such as clofibrate and birth control pills can lower your levels.

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