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. The highest levels are in liver cells. This test helps your doctor 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.

Why do you need this test?

You may need this test if you have other abnormal liver blood tests, or your doctor 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.

What other tests might you have along with this test?

You may have other liver enzyme tests. These include:

• Alanine aminotransferase (ALT).

• Alkaline phosphatase.

• Aspartate aminotransferase (AST).

• 5'-Nucleotidase.

• Creatine phosphokinase.

• Lactic dehydrogenase.

• Leucine aminopeptidase.

What do your test results mean?

Test results may vary depending on your age, sex, health history, and other things. Your test results may be different depending on the lab used. Ask your doctor 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. Levels of GGT increase with age in women and people assigned female at birth, but not in men and people assigned male at birth.

Test results that are higher than normal 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.

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 has some minor 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 your test results?

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 you get ready for this test?

You may be asked to not eat or drink anything but water for 8 hours before having this test. Tell your doctor 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.