CT Scan Prep You may wear comfortable clothing or may be required to change into a gown. Because metal affects the CT image, please do you not wear clothing with zippers or snaps. If you are scheduled for an exam of the head, earrings, glasses, hearing aids, dentures and other removable dental appliances must be removed prior to the exam. For some CT scans, especially of the abdomen or pelvis, you may be asked to drink barium (or contrast). Please come by the day before your scheduled exam, and pick up the barium. If you are scheduled for an exam with contrast or "x-ray dye," you should not eat or drink anything 2 hours before your exam, with the exception of your normal medications that can be taken with a sip of water. For some CT scans, we may need to inject contrast material into a vein to help the doctor see body structures better. If you are allergic to iodine, or have had a reaction to x-ray contrast before, you may need to be pre-medicated prior to your exam. Please inform the Radiology Department if you have an iodine allergy when scheduling your appointment. If you are diabetic and take Glucophage (Metformin) or combination medications containing Glucophage (Metformin), you may take your medicine before the exam, but cannot resume taking it for at least 48 hours after the exam is completed.