Before a colonoscopy, you'll need to clear your colon of any residue that might obscure your doctor's view during the exam. To do this you must:
Follow a special diet. You likely won't be able to consume any solid foods the day before the exam. You'll be allowed only clear liquids such as plain water, tea, and coffee without milk or cream, broth, and carbonated beverages (avoid red liquids, as that may be confused for blood). You may not be able to eat or drink anything after midnight the night before your exam.
Take a laxative. You may be instructed to take this either the night before or the night before and the morning of the procedure.
Use an enema kit. This is generally only recommended for clearing the lower colon and not the entire colon.
Adjust your medication. Make sure your doctor is aware of any medications you may be on. Particularly any blood thinners, anticoagulants, medicines used to reduce risk of blot clots or stroke; or heart medications.