GGT is an enzyme found in high level in the liver, kidneys, pancreas, heart, and brain. It is also found in lesser amount in other tissues. The GGT test is used to detect diseases of liver or bile ducts. By the way, this test can diagnose liver damage, but it can't determine the cause. So if your GGT level is elevated, you'll probably have to undergo more tests.
The normal range for GGT levels is 9–48 units per liter (U/L). Normal values can vary based on age and sex. In general, the higher the level, the greater the damage to the liver.
So, if GGT is elevated in blood it causes damage to the liver or bile ducts. Several types of liver disease can cause a rise in GGT, including: Viral hepatitis. Obstructive liver disease, like bile duct blockage or damage. It is worth considering that GGT levels are sometimes increased with the consumption of even small amounts of alcohol.
As for the low or normal GGT test result, it indicates that it is unlikely that you have a liver disease or have consumed any alcohol.