What Happens the Day Before my Colon Cancer Screening?

Learn What to Expect as You Prepare on the Day Before Colon Cancer Screening

Colonoscopy Appointment
Before your Colonoscopy. Catherine Lane / Getty Images

Learn how to prepare for colon cancer screening during the day before your scheduled examination.

The Day Before Colon Cancer Screening: What Can I Have to Eat?

The day before a colonoscopy, you will begin having only clear liquids, starting with either lunch or dinner. If you can see through the liquid, it is OK to drink, with the exception of a few liquids containing certain dyes.

You cannot have any liquids that contain red or purple dye, such as grape soda or red and purple Kool-aid.

Do not drink any juice with pulp, such as orange or grapefruit juice.

Examples of clear liquids that are OK to drink during your colonoscopy preparation include:

  • Water
  • Tea
  • Coffee, but no creamer, milk, or other dairy or non-dairy milk substitutes
  • Ginger ale
  • Apple juice
  • White grape juice
  • Plain, clear soup broth
  • Seltzer or sparkling water

Approximately three to four hours before your exam, you will stop eating and drinking everything, including clear liquids.

How is My Colon Cleared Out Before Colon Cancer Screening?

In addition to having only clear liquids, you will begin taking a strong laxative prescribed by your doctor the evening before your exam. You will be advised to drink one-half to one gallon of liquid laxative total, taken eight ounces at a time, approximately every 10-15 minutes, until all of the solution is gone.

Most people begin having bowel movements within one to four hours of beginning to take the laxative.

For some people, bowel movements begin almost immediately, so once you start this process, don’t stray too far from the bathroom!

What’s Normal When I'm Preparing for Colon Cancer Screening?

It is normal to feel bloated, to have mild chills, and to feel a little dizzy when you first begin taking the laxative.

This is due to the large amount of liquid you are drinking and the quick emptying of your colon. It is normal to have some cramping, and diarrhea is a normal part of the clearing out process, too.

It is not normal to vomit or to faint or pass out. If any of these things happen, call your doctor’s office right away.

More Important Tips on How Not to Dread Colon Cancer Screening


American Cancer Society Frequently Asked Questions About Colonoscopy and Sigmoidoscopy. Accessed: January 29, 2009.

Gastroenterology of the Rockies Colonoscopy Pep Talk. Accessed: January 29, 2009.

WikiHealth How to Prepare for a Colonoscopy. Accessed: January 29, 2009.

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