High GGT levels for a liver function test, an indication of liver disorder, is a sign that should be given attention to. It means, aside from tiredness, that an individual might also get jaundiced-skin or suffer from bellyache. It is possible that it can be due to drinking alcohol, liver disease, or some drugs. To lower these levels, try to stay away from alcoholic beverages, eat a healthy diet and have enough water. Make sure to get more accurate answers by visiting a hepatologist.