Patients scheduled to undergo a gallbladder scan need to avoid eating foods with fat in them for approximately 12 to 18 hours before the test. They should also stop eating and drinking 8 to 12 hours before the test. The emptier the digestive system is before any imaging test or medical evaluation, the better the chances are that a proper diagnosis will be reached. Do not bring any jewelry or clothes with metal accessories, as these items will need to be removed before the test can begin.