How to Prepare for a Colonoscopy

Medically Reviewed by Minesh Khatri, MD on March 25, 2023
4 min read

A colonoscopy is one of the best ways to spot or help prevent colon cancer. But many people who should have the procedure don’t. Often that’s because they’re afraid of what they have to go through to get ready for it.

Your colon has to be empty and clean for your doctor to get a proper look at it. To make that happen, you’ll have to fast and use strong laxatives beforehand. It’s inconvenient and somewhat unpleasant, but it’s temporary, and it might help save your life.

Here’s how to make the process as smooth as possible.

Your doctor is your best source of information about how to get ready. When you schedule the procedure, you’ll get instructions. Read them over well before your appointment, and call your doctor if you have any questions.

Clear your schedule for the evening before and the day of your colonoscopy, and make plans for someone to go with you the day of the colonoscopy.

Shop for some key supplies several days ahead, too. Your list may include:

  • A prescription or over-the-counter laxative specified by your doctor
  • Low-fiber food
  • Sports drinks, juices, and broths
  • Moist wipes
  • Diaper cream

You can help the cleansing process by eating light 3 or 4 days before the procedure. Doctors recommend low-fiber foods that are easy to digest and leave your system quickly.

You can have:

  • White bread, pasta, and rice
  • Well-cooked vegetables without skin
  • Fruit without skin or seeds
  • Lean meat, chicken, or fish
  • Eggs

Don’t eat:

  • Seeds, nuts, or popcorn
  • Fatty foods
  • Tough meat
  • Whole grains
  • Raw vegetables
  • Fruit with seeds or peel
  • Corn, broccoli, cabbage, beans, or peas

At this point you should stop taking vitamins or other supplements. Ask your doctor whether and when you should stop taking any prescription medicines you use regularly, and any over-the-counter anti-inflammatory or blood thinning meds you may use.

The day before your procedure you can’t eat anything solid. You should only consume clear (see-through) liquids.  It is important to stay hydrated by drinking lots of clear liquids, such as sports drinks, clear juice like apple and white grape, and clear broth. Soda is OK, and so are coffee and tea, but without cream. You can have gelatin and ice pops, but stay away from anything colored red, blue, or purple. The dyes can discolor the lining of the colon and make it harder for the doctor to see. Also avoid alcohol and drinks you can’t see through, like milk or orange juice.

Two to four hours before the procedure, be sure not to drink or eat anything (please consult your doctor on the exact time to stop consuming clear liquids).

The night before your colonoscopy you’ll take strong laxatives to clear your digestive tract. The method recommended for most people is called split dosing. You’ll drink a half-gallon of liquid laxative in the evening. Then you’ll get up about 6 hours before your appointment to drink another half-gallon.

You probably won’t enjoy the taste of the solution, but there are tricks to help get it down:

  • Mix it with something flavored, like a sports drink or powdered drink mix.
  • Keep it well chilled.
  • Drink it through a straw placed far back on your tongue.
  • Follow it with a sip of something good tasting.
  • Suck on a lemon slice or piece of hard candy after drinking.

Once the laxative starts working, you’ll have frequent, forceful diarrhea. You may have cramps and bloating. If you have hemorrhoids, they may become irritated. You may also feel nauseated and even vomit. If so, your doctor may recommend you take a short break.

Try these tips to make yourself as comfortable as possible:

  • Stay in the bathroom -- bring something to entertain yourself, like a book, television, or laptop.
  • Apply diaper cream before the diarrhea starts.
  • Use moist or medicated wipes to clean yourself.

The purge process may still be happening as you head to your appointment. If you’re worried about having an accident, consider wearing adult diapers and pack extra clothes.

Your stool should look like urine or clear water if you have completed the process appropriately and it has worked effectively. 

The process isn’t easy, but remind yourself this is a smart step to protect your health. If you prepare well, your doctor will be able to see what they need, and your colonoscopy will go faster. If your results are good, it may be 10 years before you have to go through it again.