A two-day liquid diet is usually not enough preparation for a colonoscopy. Preparation generally involves consuming a clear liquid diet starting the day before the procedure and taking a bowel-cleaning preparation, explains Harvard Health Publications. It's best to direct specific questions regarding colonoscopy preparation to the doctor performing the procedure.
Taking the bowel-cleaning preparation is important to completely empty the contents of the bowel. An inadequate bowel prep can cause polyps and lesions to be missed, lead to a longer procedure or cause the procedure to be cancelled and rescheduled, according to Harvard Health Publications. Starting a low-fiber diet free of whole grains, nuts, seeds and raw fruits and vegetables a few days before the colonoscopy is also recommended.