How to prep for a successful colonoscopy

If you really want to know what’s going on inside your colon, don’t show-up for a colonoscopy without a clean colon.

Many say that preparing for the colonoscopy is the worst part of the entire exam. But, it just so happens that it’s also the most important part.

If the prep is done right, it’s easier for your doctor to see not only big polyps but also flat polyps, which can be harder to spot if your colon is not completely clean.

Polyps are small growths on the lining of the colon that can become cancer.

It’s especially important to find those flat polyps because they tend to grow into cancer faster than any other polyp type.

Another great benefit to having a clean colon is that your doctor can spend more time carefully examining the colon instead of trying to wash away any stool that’s left.

If you go in for your colonoscopy with a semi-clean colon, one of two things will happen – the doctor won’t see the insides of the colon clearly, so you’ll have to redo the prep and come in for a repeat colonoscopy.  Or, even worse, your doctor may miss a polyp during the exam—a hidden polyp with the potential to become cancer.

Steps to a successful prep

Your goal should be to get your colon as clean as the palm of your hand before you go in for your colonoscopy. Here’s how to reach that goal.

On the day before your exam:

  • Eat plain cereal with milk for breakfast.
  • Eat a light lunch consisting of soups without vegetables.
  • Drink clear liquids only.
  • Do not eat solid foods.
  • Drink a large volume of the special cleansing solution and/or special oral laxatives recommended by your doctor.
    • Split the solution dose.
    • Drink the first two liters on the evening before the exam.
    • Drink the second two liters four to six hours before the exam. This last step is critical to getting a really thorough clean.

Get a personalized prep plan from your doctor

Talk to your doctor about what you can and can’t eat before the exam. Ask your doctor about what’s the best way to clean your colon.

If you generally have problems with constipation, discuss this with your doctor. Your doctor may suggest drinking magnesium citrate so that you are not constipated on the day you begin taking the cleansing solution. Do not take Metamucil® and don’t eat foods with small seeds, such as kiwi, cucumber or bread with sesame seeds. These foods can disrupt the cleansing process.

Remember to inform your doctor about any medications you’re taking, particularly aspirin products, non-steroidal anti-inflammatory medicines, arthritis medications, blood thinners, insulin or iron products.

Most medications can be continued as usual, but some medications can interfere with the preparation or the examination. Be sure to mention to your doctor any allergies you may have to medications.

If you have diabetes, ask your doctor if you need to adjust your insulin or other medicines to control blood sugar.

Gottumukkala S. Raju is a gastroenterologist at The University of Texas MD Anderson Cancer Center.

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  • Mike Bechtel

    Dr. Raju,
    This is a great explanation of how to prepare for a colonoscopy.  I work for a company that builds patient communication tools to engage and activate patients in their care.  Our content is completely “prescribable” and trackable and is meant to span the continuum of care.  Check out this link to view our colonoscopy program. 

    Please let me know if you have any questions or comments!
    Best, Mike

  • Kathleen Summers

    Dear Dr. Raju,

    Do you have any experience with the physiological salt water preparation for colonoscopy? Both patients I’ve had who were bent on natural methods (as opposed to commercial preparations from industry) told me their gastroenterologists were extremely happy with their prep. 

    My understanding is that it was the preferred way to cleanse until less salty tasting, branded products came along.

    I would appreciate it if you would share your thoughts on, and experience with, this technique.

    Chambers CE, Carter HG. Saline lavage: a rapid, safe, effective method of whole-gut irrigation for bowel preparation. South Med J. 1978 Sep;71(9):1065-6. PDF (162 KB)Levy AG, Benson JW, Hewlett EL, Herdt JR, Doppman JL, Gordon RS Jr. Saline lavage: a rapid, effective, and acceptable method for cleansing the gastrointestinal tract.Gastroenterology. 1976 Feb;70(2):157-61.Crapp AR, Tillotson P, Powis SJ, Cooke WT, Alexander-Williams J. Preparation of the bowel by whole-gut irrigation. Lancet. 1975 Dec 20;2(7947):1239-40.

  • Anonymous

    Having actually had one, besides the above, let me add: apply Desitin (yup, the diaper rash stuff) as needed. After drinking the mag citrate and the Go-Lytely stuff (and whatever else they want you take), you’re going to need it. 

  • Judy Stephenson

    I would like to recommend a product for colon cleansing which is excellent.  It is called X-Prep.  It is a liquid senna product made by Purdue. The experience for the patient is minimal cramping and predictable evacuation.  My friend who had colon cancer at age 42 and many follow up scopes swears that  X Prep helped her get over the fear and hassle of the colon prep.  Pharmacies sometimes stock it but they will get it in stock for the patient.  The cost is more around $20 compared to the citrates but the comfort is worth it.

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