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Preparing for a Colonoscopy

Before a colonoscopy procedure, the contents of the colon have to be emptied. This is usually done through a liquid only diet for 24 hours as well as drinking a solution to help clear the bowels. If the bowel prep is not completed correctly, polyps and lesions can be missed and the entire procedure may have to be repeated.

Below is the most common bowel preparation for colonoscopies. Your physician at St. Joseph’s will discuss specifics for your procedure.

Preparing for a Colonoscopy


On the day before and up to the procedure, consume clear liquids only: broths, soft drinks, tea and coffee (with no milk or creamer), clear juices or Jell-O (b)ut no red, blue, or purple coloring. You may also be asked to avoid nuts, seeds, hulls, skins, or other insoluble fiber for a day or more before beginning clear liquids.

Polyethylene glycol

This is an electrolyte-balanced solution consumed in large amounts (4) liters, or about 1 gallon the evening before a colonoscopy. You will need to drink 8 ounces every 10 minutes until the bowel’s output runs clear or the solution is completely consumed. In another approach, the dose is divided into 3 liters the night before and 1 liter the morning of the colonoscopy.

Useful Tips for a Colonoscopy

  • Make sure you receive your colonoscopy prep instructions well before your procedure date, and read them completely as soon as you get them.
  • Pick up some medicated wipes and a skin-soothing product such as Vaseline or Desitin.
  • Arrange for the time and privacy you need to complete the prep with as little stress as possible.
  • Water can get boring, so keep a variety of clear liquids on hand.
  • To make a bad-tasting liquid prep like PEG easier to swallow, try one or more of the following:
    • Add some Crystal Light or Kool-Aid powder (a)gain, not red, blue, or purple
    • Add some ginger or lime
    • Drink it chilled
    • Drink it through a straw placed far back on your tongue
    • Hold your nose and drink it as quickly as possible
    • Suck on a hard candy after each glass.
  • Wear loose clothing, and stay near or in the bathroom.