Diet Before Colonoscopy Bowel Preparation

Karen Frazier
Reviewed by Terri Forehand RN
Diet Before Colonoscopy

Preparing for a colonoscopy is important. Eating the right foods and following bowel prep instructions carefully cleans out your colon, giving your doctor a clear view to see your colon walls during your procedure. Without the unobstructed view created by appropriate colon preparation, your physician may miss polyps or cancerous lesions.

Diet Before Colonoscopy

To prepare colon for the procedure, your doctor or nurse will provide information regarding a diet. According to Colon Cancer Resource, you should begin to change your eating about four days before the procedure is performed. The diet reduces or totally eliminates fiber and will include food like the following:

  • Boiled chicken (no skin)
  • Cheese
  • Eggs
  • Skinless potatoes
  • Steamed white fish
  • White bread

According to the Mayo Clinic, some diets used to prepare patients for a colonoscopy call for the elimination of all solid food a day or two prior to the colonoscopy, with a clear liquid diet the day before the procedure. This is a precautionary measure taken to make sure your bowels are empty. Your doctor will very likely require you do not take in any food or drink after midnight on the day before the procedure.

Foods to Avoid

The following list of foods should not be eaten in the days leading up to your colonoscopy because they are high in fiber:

woman with glass

Liquids to Be Avoided

In preparation for a colonoscopy, your diet should include plenty of liquids. However, there a some that should be avoided:

  • Milk
  • Milk-based drinks
  • Foods and beverages colored red or purple (Some doctors ask you to avoid orange-colored dyes as well.)

Medications and Supplements

Another thing to consider when preparing for a colonoscopy is what supplements or medications you take. If you take an iron supplement, you must also discontinue it, even if it is an ingredient in your multi-vitamin. Iron is constipating and may harm your bowel preparation. Likewise, iron may cause swelling of the colon walls, which can limit the view through the endoscope. You also need to discuss any and all supplements, herbs, and medications you take with your doctor. Some of these supplements may inhibit blood clotting and could lead to bleeding during the procedure. Your doctor will provide specific recommendations about which supplements, herbs, and medications you need to stop taking.

What to Eat the Day Before Your Colonoscopy

While the change you make to your diet prior to a colonoscopy starts three or four days prior the procedure, on the day before, you need to switch to a clear liquid diet according to the National Digestive Diseases Information Clearinghouse. This helps prepare your body for the effect of the laxative you'll be given to totally clear your bowels before the procedure. Include plenty of fluids in your diet the day before you go in for your colonoscopy because the laxatives can promote dehydration. To avoid this problem, make it a point to drink your fluids. It's best to drink something every hour if possible. The liquids you can drink the day before include the following:

  • Coffee with nothing added
  • Fat-free broth
  • Sports drinks such as Gatorade
  • Tea with nothing added
  • Water
  • Honey
  • Non-pulp or strained, light-colored fruit juice (white grape juice, apple juice)
  • Clear soda (like Sprite)
  • Plain gelatin
  • Ice pops

The Day of the Procedure

You should not eat any food on the day of the procedure, and you shouldn't eat or drink anything between two or three hours before your colonoscopy. Once the procedure is finished, your doctor will give you instructions about resuming your normal diet. Sedation is usually given during the procedure, so your doctor may want you to start with liquids or soft foods to avoid nausea and vomiting from the sedation medication. Most people can begin to eat normally within a few hours.

Importance of a Clean Colon

The whole reason it's important to follow a diet such as this preceding a colonoscopy is that the procedure can only be done if your bowels are empty. If you follow the diet instructions your doctor gives you, you'll make his job easier as the endoscope can freely move through a clean colon while providing a clear picture. Preparing your body for a colonoscopy can be unpleasant, but it's an important part of preserving your health.

Diet Before Colonoscopy Bowel Preparation