The best way to prepare for a gastrointestinal endoscopy depends on whether the doctor plans to perform an upper GI endoscopy or a lower GI endoscopy. The American Gastroenterological Association defines an endoscopy as a procedure used to look inside part of the body.
A gastroenterologist performs an upper GI endoscopy to look at the stomach, esophagus and first part of the small intestine, notes the American Gastroenterological Association. In contrast, a lower GI endoscopy helps the doctor visualize the large intestine, according to Beth Israel Deaconess Medical Center. Another name for a lower GI endoscopy is colonoscopy.
Prior to undergoing an upper GI endoscopy, a patient should refrain from eating for eight to 10 hours, recommends the American Gastroenterological Association. The patient should also provide a list of current medications and make staff members aware of any medical problems that might affect the outcome of the procedure.
The preparation instructions for a lower GI endoscopy are much more detailed. Because fecal matter can obstruct the physician's view of the colon, the patient must empty his colon completely by taking oral medication, laxatives or enemas. Alcohol, milk and solid foods are prohibited on the day before the procedure. Ice pops and gelatin are allowed, but only if they are not red, states Beth Israel Deaconess Medical Center.