Be sure your doctor is aware of any medicines you are taking, as you may need to change how you take them before the test. The colon and rectum must be empty and clean so your doctor can view their inner linings during the test. You will need to take laxatives (liquids, pills, or both) the day before the test and possibly an enema that morning. Your doctor will give you specific instructions. It is important to read these carefully a few days ahead of time, since you may need to shop for special supplies and get laxatives from a pharmacy. If you are not sure about any of the instructions, call the doctor's office and go over them step by step with the nurse. Many people consider the bowel preparation to be the most unpleasant part of the test, as it usually requires you to be in the bathroom quite a bit.
You may be given other instructions as well. For example, your doctor may tell you to drink only clear liquids (water, apple or cranberry juice, and any gelatin except red or purple) for a day or 2 before the exam. Plain tea or coffee with sugar is usually okay, but no milk or creamer is allowed. Clear broth, ginger ale, and most soft drinks or sports drinks are usually allowed unless they have red or purple food colorings, which could be mistaken for blood in the colon.
You will likely also be told not to eat or drink anything after midnight the night before your test. If you normally take prescription medicines in the mornings, talk with your doctor or nurse about how to manage them for the day.You may need to arrange for someone to drive you home from the test because the sedative used during the test can affect your ability to drive. Depending on the medicines that are used, some doctors require that someone drive you home.