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Clear liquids like water are consumed prior to a colonscopy

A colonoscopy is a test in which a small camera affixed to the end of a lighted thin, flexible tube is inserted into the colon for examination. Colonoscopies are used, according to the American Cancer Society, to screen patients for problems such as polyps, colon cancer and bleeding. This is a relatively painless procedure that the patient must prepare for by cleaning solid wastes out of the colon. This will provide the doctor with a full view of the colon's inner surfaces.

Step 1

Consume only clear liquids and foods the day before and the day of the test, until the colonoscopy is completed. Clear liquids include black tea and coffee, broths, grape, apple or cranberry juices, and clear soft drinks like ginger ale and lemon lime soda. Clear foods include flavored gelatin and frozen flavored ices. If you tend to have problems with constipation, Washington Hospital Center recommends that you follow this diet for two days prior to the test. In some cases, a patient will also be asked to refrain from eating nuts, seeds and similar indigestible fibers for one or more days prior to the colonoscopy.

Step 2

Drink a gallon of polyethylene glycol (PEG) electrolyte solution over a four hour period the evening before the test. According to Harvard Medical School, 8 oz. of the solution should be consumed every 10 minutes. The colon is considered completely clean once the patient's bowel movements are clear. In some cases, 3 liters of the solution are consumed the night before the test and the final liter is consumed the morning of the test.

Step 3

Consume two small doses of oral sodium phosphate (OSP) mixed in 8 oz. of clear fluid taken 10 to 12 hours apart instead of taking the PEG if your doctor advises this. You must also drink at least 16 oz. or more of clear liquid after each dose of oral sodium phosphate. This solution can cause you to become dehydrated so it is necessary to maintain consistent intake of fluids in the days prior to and the day of the colonoscopy.

Step 4

Take four laxative tablets the evening before the procedure as an alternative to steps 2 and 3 if your doctor prefers that you use this method for cleansing your colon. This should be followed by a qt. of apple juice to help the laxative effect. You can purchase laxative tablets over the counter from your local pharmacy.

Step 5

Administer an enema the morning of the exam if it appears that the bowels are not completely clear. Use this treatment approximately one to two hours prior to the colonoscopy. The enema should be administered into the anus when the patient is laying on his left side, with his left leg straightened and his right leg drawn up towards his chest in a 45 degree angle. Squeeze the entire content of the enema bottle into the rectum and add another full bottle of warm water immediately afterward. The patient should lie still for five minutes and then evacuate his bowels into the toilet.

Things You'll Need

  • Polyethylene glycol (PEG) electrolyte solution or oral sodium phosphate (OSP) or laxative tablets

  • Enema (optional)


Be sure to also purchase medicated wipes made for hemorrhoids, because the significant amount of laxatives being used can cause soreness and irritation in the rectal area.


Don't make plans the days preceding or the day after the colonoscopy. While the test itself doesn't take long and only causes minor discomfort, the after effects of the laxatives, enemas and liquid diet can cause you to have loose bowels for a day or two after the test.

Is This an Emergency?

To reduce the risk of spreading COVID-19 infections, it is best to call your doctor before leaving the house if you are experiencing a high fever, shortness of breath or another, more serious symptom.
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