The day before a colonoscopy, most patients must switch to a clear liquid diet consisting of water, broth and other see-through liquids, according to the Harvard Medical School Family Health Guide. Gelatin and ice pops are usually acceptable foods to consume at this time as well.
The purpose of the clear liquid diet is to keep the stomach and intestines clean while limiting the stress on the digestive system, according to Mayo Clinic. It helps keep the body hydrated while the patient prepares for the test. The patient's doctor may make specific modifications to the diet in preparation for the test. A diabetic patient needs to inform his doctor of his health condition. Usually, a diabetic must consume 200 grams of carbohydrates per day while on the liquid diet. The patient should spread the carbohydrates throughout the day and monitor his blood sugar closely.
The Harvard Medical School Family Health Guide indicates patients must avoid liquids containing red, blue or purple dyes when preparing for a colonoscopy; however; coffee, tea and most sodas are acceptable. Before and during the bowel preparation, which involves taking laxatives to clear the colon, patients should increase their fluid intake. Adding flavored drink mix to the laxative makes it more palatable.
The purpose of a colonoscopy is to let the doctor search for lesions, polyps and other signs of trouble in the bowel. As a result, the bowel needs to be as clear as possible before the examination begins. Beginning 3 or 4 days before the colonoscopy, the patient should eliminate as much fiber as possible from the diet, staying away from raw produce, dried fruit, seeds, nuts and whole grains, according to Harvard Medical School.