Your stomach and duodenum must be empty for the procedure to be accurate and safe. You will not be able to eat or drink anything after midnight the night before the procedure, or for 6 to 8 hours beforehand, depending on the time of your procedure. Also, the physician will need to know whether you have any allergies, especially to iodine, which is in the dye. You must also arrange for someone to take you home—you will not be allowed to drive because of the sedatives. The physician may give you other special instructions.