How to Prepare for a Colonoscopy

Medically Reviewed by Zilpah Sheikh, MD on May 01, 2024
Written by Alyson Powell Key
7 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.

Before your procedure, you'll go through a process called colonoscopy preparation, and it could begin a few days ahead of time. 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

Why do doctors prescribe laxatives before colonoscopy?

Laxatives help clean out your bowels so your doctor can see the inside of your colon. They may come as a prescription or be bought over the counter. Preparing for a colonoscopy isn’t easy, but remind yourself that this is a smart step to protect your health. Not preparing well could mean your doctor will postpone or cancel your colonoscopy, or you'll need to have another one.

But if you prepare well, your doctor will be able to see what they need, and your colonoscopy will go faster. And if your results are good, it may be 10 years before you have to go through it again.

Your bowels must be empty so your doctor can see the inside of your colon more clearly. You can help the bowel cleansing process by eating light 3 or 4 days before the procedure. 

Recommended colonoscopy prep diet

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.

The day before your procedure, you can’t eat anything solid. You should only consume clear (see-through) liquids. 

Recommended colonoscopy prep drinks

Staying hydrated is important -- drink 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).

When should I start prep for a 7 a.m. colonoscopy?

You'll drink the laxative the evening before your colonoscopy and will stop eating solid food after breakfast the day before.

You'll take strong laxatives the night before your colonoscopy to clear your digestive tract. The method recommended for most people is split dosing. You’ll drink a half-gallon of liquid laxative in the evening, and 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.

What does colonoscopy prep poop look like?

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

Polyethylene glycol (PEG) kits

Bowel prep for colonoscopy often uses a laxative called polyethylene glycol (PEG). It comes as a powder, and you mix it with lots of water. It may include electrolytes, or you can take it with a sports drink.

PEG bowel preps work well for colonoscopy prep, and they're gentle on your intestines, which is especially good for people with IBS symptoms. But they do require a lot of drinking (up to 4 liters), and the taste can be hard to handle.

Oral sodium phosphate (OSP) kits

These colonoscopy prep medications in tablet form have sodium phosphate and other ingredients. You'll drink less water with them, around 3 liters instead of the typical 4. While they may work well, OSP medicines can cause stomach-related side effects.

Saline-based kits

Saline-based laxatives use sodium phosphate (NaP) as the active ingredient, as well as minerals like potassium and magnesium. These are often in tablet form and can substitute liquid bowel prep.

This type of bowel prep can be easier to swallow for people who struggle with PEG preps. But a saline-based laxative may irritate your intestines if you have an inflammatory GI disease. It's also unsafe for people with a higher chance of fluid-electrolyte imbalances due to certain health conditions or medications.

Hybrid kits

If you're worried about bloating, cramping, gas, or other side effects, talk to your doctor about a hybrid bowel prep. These use an osmotic laxative (the active ingredient that makes you poop) along with one that may cause fewer side effects.

What colonoscopy prep is best for kidney patients?

If you have kidney disease, a PEG prep is your best bet to avoid health problems related to losing fluid and electrolytes.

After your colonoscopy, you might feel bloated or gassy for a few hours. It's also normal to see a bit of blood in your first bowel movement after the exam. But if you keep seeing blood or have ongoing stomach pain or a fever, contact your doctor.

What is the easiest colonoscopy prep to tolerate?

It varies from person to person. For example, people with certain health conditions, like kidney, heart, or gastrointestinal disease, may tolerate one prep more than another. Talk to your doctor about which option is best for you.

Should you expect weight loss after colonoscopy?

Yes, but it's water weight, and you'll probably gain it back after the procedure.

 

 

A colonoscopy is crucial for detecting or preventing colon cancer, but many avoid it due to the preparation process. To make sure you have a successful colonoscopy, your colon needs to be empty. This calls for a change in your diet and strong laxatives beforehand. Adjust your diet to include light, low-fiber foods leading up to the procedure, and stop certain medications and supplements as your doctor advises. The day before, drink only clear liquids, avoiding colored ones. The night before, you'll take strong laxatives in two doses. If you've done your prep right, your poop should be clear by the end.

How painful is a colonoscopy?

You'll likely be asleep or sedated during your colonoscopy, so you won't feel anything. If you choose lighter sedation or none at all, you're more likely to feel discomfort or pain during the procedure.

Do they put you to sleep for a colonoscopy?

Most colonoscopies in the U.S. happen while patients are asleep or heavily sedated. 

At what age should you get a colonoscopy?

Experts suggest that most people start colon cancer screening at age 45. You may need screening at a younger age if you have inflammatory bowel disease or a family history of colorectal cancer or colorectal polyps. 

How long does a colonoscopy usually take?

The procedure normally takes about 30 to 60 minutes.