Colonoscopy Prep

Colonoscopy prep (also called bowel preparation or bowel prep) is the process of emptying and cleaning out your colon before a colonoscopy. This usually involves following a special diet and drinking a laxative solution (a colonoscopy prep drink).

A clean colon is important so your healthcare provider can clearly see the lining of your colon. Signs of colorectal cancer, like polyps, often stick to the inside walls of your colon. Poop can hide these areas and make it harder for your provider to spot problems. Not having a clear colon on the day of your procedure can lead to a canceled procedure or inaccurate results.

There are different bowel prep kits. These kits are the specific instructions and products your healthcare provider gives you to complete the prep. They use different combinations of laxatives and fluids to fully empty your colon.

Bowel prep usually includes:

• Osmotic laxatives: The main medicine in bowel prep is a laxative that pulls water into your colon. This makes your stool softer and adds more volume. It also stretches the wall of your colon, which triggers muscles to squeeze and push poop out.
• Clear liquids with electrolytes: You also drink clear fluids during prep to prevent dehydration. These often include electrolyte drinks, like clear sports drinks. Sports drinks shouldn’t be red or purple because these colors can look like blood in your colon.

Always follow the instructions for the colon prep kit you receive. Colonoscopy prep instructions tell you exactly when to begin your kit. Most kits use “split dosing.” This means you take one dose the day before your procedure and one dose around four to six hours before your procedure.

What are the different types of colonoscopy prep kits?

Colonoscopy preparations fall into two basic categories based on the type of laxative they use. You’ll begin taking your laxative bowel prep the afternoon or evening before your colonoscopy. The exact timing will depend on the formula you’re taking and what time your colonoscopy is scheduled for.

Polymer-based formulas (PEG)

The most prescribed bowel prep formulas use a polymer-based laxative known as polyethylene glycol 3350 (PEG). PEG formulas are typically in powder form and mixed with large volumes of water or sports drinks.

PEG-based colonoscopy prep drink names include:

• Golytely®, Nulytely®, Trilyte® or Colyte®
• MiraLAX®
• HalfLytely®
• GaviLyte®
• MoviPrep®

Always read the instructions fully and carefully before you start your prep. Contact your provider with any questions you have.

Saline-based formulas (NaP)

Saline-based formulas use sodium phosphate (NaP) to help you poop. Some NaP products are liquids that come already mixed in bottles. Others are tablets or pills that you take with a lot of clear fluids.

NaP-based colonoscopy prep brand names include:

• Clenpiq®
• Suprep®
• Prepopik®
• OsmoPrep®
• SUTAB®

Remember, you must follow the directions for your bowel prep to work correctly. Contact your provider if you’re unsure about what to do or when to do it.

Am I at risk of complications from certain types of bowel prep formulas?

All bowel prep kits have pros and cons. Your healthcare provider uses your health history to choose the right one for you. Be sure to tell them about any medical conditions you have and about current medications so they can make the right choice.

How many hours before your colonoscopy do you start your prep?

It depends on the type of kit you’re using. Most start the day before your colonoscopy. Be sure to read the instructions several days before your procedure. This gives you time to prepare. You may need to buy supplies like clear liquids and sports drinks.

What to eat before your colonoscopy

Your healthcare provider will give you specific eating/drinking instructions for the days just before your colonoscopy. They may adjust certain medications before your procedure. Share your full list of medications with your provider when you schedule your colonoscopy.

Three days before your colonoscopy

You’ll eat a low-fiber diet starting two or three days before your colonoscopy. You should stop eating things like seeds, nuts, beans, raw vegetables and popcorn. These foods tend to stick to your colon.

The day before your colonoscopy

You'll follow a clear liquid diet on the day before your colonoscopy. Don’t eat any solid foods.

Here's a list of drinks you can have:

• Water, tea, and clear sodas, like ginger ale or Sprite®
• Tea and black coffee (no cream or milk)
• Chicken or vegetable broth/bouillon
• Sports drinks (not red, purple or orange)
• Gelatin, like Jell-O® (not red, purple or orange flavors)
• Pulp-free fruit juices like apple juice or clear grape juice

Do not drink any of the following:

• Alcohol
• Milk or non-dairy creamers
• Noodles or vegetables in broth
• Juices with pulp
• Beverages that are dark colored (other than black coffee)

To avoid your colonoscopy being canceled, follow your provider’s instructions exactly as they’re given to you.

When to stop drinking before a colonoscopy

You usually stop drinking clear liquids a few hours before your colonoscopy (usually two to four hours before). Your provider should include the time to stop drinking clear liquids in their instructions.

How long does it take a bowel prep to kick in?

It depends on the formula you're taking. PEG-based bowel prep may take one to three hours. NaP-based bowel prep may take three to six hours to start.

Contact your provider if you’re constipated and not pooping several hours after you begin. You might need to take extra steps to get things started.

What if I'm still pooping before my colonoscopy?

Your prep is done when your poop is a clear yellow liquid that you can see through. If you start your prep on time, you shouldn’t be having many bowel movements by the time you arrive for your procedure. Some people choose extra protection, like pads or protective underwear, just in case of accidents.

When should I contact my healthcare provider during my colonoscopy prep?

Call your healthcare provider if:

• You forgot to stop eating or to start your prep on time
• You get sick and need to reschedule
• You’re not pooping after five to six hours
• You’re having severe abdominal pain
• You can’t keep fluids down or you’re vomiting
• You think you won’t be able to finish the bowel prep