A high GGT level can indicate a disease of the liver or bile duct as well as diabetes, heart failure and disease of the gall bladder, lung or pancreas. The normal range for GGT is 0 to 51 IU/L.
The GGT test is currently the most sensitive enzymatic indicator of liver disease, according to the Mayo Clinic. Levels five to 30 times normal indicate obstruction of the bile duct. The test is more sensitive than other laboratory measures in detecting obstructive jaundice, infection of the bile duct and inflammation of the gall bladder. It is less useful in diagnosing infectious hepatitis.
The test measures the amount of the enzyme gamma-glutamyl transpeptidase, or GGT, in the blood and is also used to screen for and monitor alcohol abuse. The GGT test is often used in combination with other tests, such as alkaline phosphatase, alanine transaminase and bilirubin, to distinguish between liver, bile disorders and bone disease. An elevated GGT level is also correlated with an increased risk of cardiovascular disease, according to a study published in the peer-reviewed journal Preventive Cardiology.
Alcohol and some drugs, such as phenytoin and phenobarbital, can increase GGT levels. Drugs that can decrease GGT levels include birth control pills and the lipid-lowering agent clofibrate.