Liquids and laxative. On the before the colonoscopy, you will be on a liquid diet all day and either drink an electrolyte solution or take a series of tablets-both of which will induce diarrhea. The prep usually takes 3 to 4 hours to run its course.
Variable. Usually a clear liquid diet for the 24 hours prior to the procedure and some type of laxative to effectively clean the colon of all stool to allow a thorough and accurate exam. Check with the doctor performing the colonoscopy as to which prep he prefers or recommends.