GGT, Gamma-Glutamyl Transpeptidase

This is a test to screen for liver disease; alcohol related liver damage; and to differentiate between liver and bone disease as a cause for elevated alkaline phosphatase (ALP). GGT is an enzyme found mainly in the liver; it is very sensitive to changes in liver function. It is normally present in low levels in the blood. When the liver is injured or obstructed, the GGT level rises. It is the most sensitive liver enzyme in detecting bile duct problems.


A blood sample is obtained by inserting a needle into a vein in the arm.


Normal values depend on many factors.

  • Male and female over age 45: 8-38 units/L or 8-38 international units/L (SI units)

  • Female under age 45: 5-27 units/L or 5-27 international units/L (SI units)

  • Elderly: Slightly higher than adult level

  • Child: Similar to adult level

  • Newborn: 5 times higher than adult level

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.