The Gamma-Glutamyl Transpeptidase (GGT) test is used to measure the amount of the enzyme GGT in your blood. This enzyme is present mainly in the liver and is also present in various other organs such as the gallbladder, spleen, pancreas, and kidneys. A high level of GGT can be a sign of liver disease or bile duct injury/blockage. The test is also used for diagnosis of liver diseases. Your doctor may suggest the test if you have symptoms like fatigue, weakness, jaundice, loss of appetite, abdominal pain or swelling, dark coloured urine, nausea and vomiting. This test may also be used to differentiate liver and bone disease if ALP levels are elevated. In liver diseases both GGT and ALP levels are elevated and in bone diseases only ALP levels are elevated.