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5 doctor-approved colonoscopy prep tips 

5 doctor-approved colonoscopy prep tips (Getty Images)

Being prepared for this cancer-detecting procedure will help you and your doctor. Follow these pro tips.

Have you recently scheduled a colonoscopy? If so, congratulations on doing something good for your health. Staying on top of this preventive cancer screening is a key wellness move as you get older.  

It’s likely that you’ve had this screening test in the past. The American Cancer Society recommends a colonoscopy every 10 years from age 45 to 75.1 You might have started earlier if you have a family history of colon cancer.2 

And if you have had one, you probably remember the prep part. The night before, you drink a special formula to clean out your bowels. You might be dreading that a bit, but there are ways to make it easier.  

With the right prep, you can help make your appointment a success. (And your doctor will thank you, too.) Here’s a refresher on why colonoscopies are important, plus doctor-approved prep tips to ensure a smooth test. 

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Colonoscopy basics 

A colonoscopy is one of the best ways to check for colon cancer. Your doctor uses a thin, flexible lighted tube with a small video camera on the end to examine your rectum and colon.3  They look for polyps (abnormal growths) inside your colon, which can develop into cancer.4 Your doctor can remove polyps during the procedure. A colonoscopy can also find colon cancer early. 

Prepping for a colonoscopy involves a special diet to clean out your colon. That’s so your doctor can get the clearest view of it. Sometimes, polyps can be sneaky, says Niren Jasutkar, MD. He's a gastroenterologist with Optum in Secaucus, New Jersey. The cleaner the inside of your colon is, the more likely it is that your doctor will be able to see everything, he adds. 

You do this by avoiding certain foods and taking a laxative before the test.5 A laxative helps you go to the bathroom and clean out your bowels. It comes in different forms, including liquids and pills.6 Use these tips to help with your prep.  

Tip #1: Think ahead 

Start getting ready at least one week before your colonoscopy. Your doctor will have already given you instructions on how to prepare for the procedure, says Dr. Jasutkar. That’ll include things like: 

  • When you can pick up your bowel prep kit from the pharmacy. It’s good to take care of this a week ahead of time, in case the prescribed medication is out of stock at your pharmacy or there are insurance delays, says Dr. Jasutkar. 
  • What you can and can’t eat or drink in the days leading up to the procedure  
  • When and how to drink that laxative (or in what order to take those pills)  
  • What you can and can’t eat or drink on the day before and of the procedure 
  • Any medications you should avoid taking 

Some patients wait until a day or two beforehand and wind up in a last-minute rush to prepare for it, says Dr. Jasutkar. 

By preparing ahead of time, you’ll have plenty of time to get comfortable with the kit’s instructions (or any that your doctor gives you). And you can go to the grocery store to stock up on items for your prep diet.  

Plus, you might find you have questions or concerns for your doctor before the procedure. That’s fine. Don’t be afraid to call their office or send them a note through your patient portal, if that’s an option. Ask them anything: That’s what they’re there for.  

Tip #2: Track what you’re eating 

Your doctor may fill you in on the foods you can and can’t eat before your procedure. But for a quick run-through, here’s what your prep diet may look like: 

Two to three days before: Your doctor may ask you to cut back on high-fiber foods.6 This will start two to three days or longer before your colonoscopy, says Dr. Jasutkar. These foods include: 

  • Beans 
  • Nuts  
  • Raw vegetables  
  • Seeds  
  • Whole grains  

The day before: On the day before, you’ll be asked to stick to clear liquids only.7 This ensures you don’t have food left behind in your body. It’s also easier to clear out of your colon. 

Sometimes patients are confused about what a clear-liquid diet means, says Dr. Jasutkar. It means only eating or drinking clear liquids and certain light-colored beverages. These include:7 

  • Clear broth (such as vegetable or chicken, with no chunks) 
  • Coffee and tea (without milk or cream) 
  • Gelatin (without fruit or red or purple dye)  
  • Clear, light-colored fruit juices without pulp (such apple juice) 
  • Light-colored sports drinks (avoid red or purple ones) 
  • Water 

The night before: You may not be able to eat or drink anything after midnight.3 That might not be so fun. But think of it this way: After the procedure, you can have a healthy, celebratory meal. 

Looking for an Optum doctor to talk to about preventive screenings? Our providers are here to help you reach your health goals. Find an Optum doctor

Tip #3: Drink your laxative (or swallow your pills) 

Your doctor will let you know when to start taking the medicine. A bowel prep kit is a laxative drink used to wash out your colon, Dr. Jasutkar says. (Some doctors may also prescribe a series of pills that have a similar effect.)  

You’ll usually start drinking or taking it the evening before your procedure. Then you’ll finish it the next morning, at least four hours before the exam.8   

There are different types of bowel prep kits. Some include a liquid laxative and a container to mix the laxative with water. And others are premixed, adds Dr. Jasutkar. The pills typically come with a small pitcher you fill up with water and drink over a series of hours. 

Laxative mixtures might not taste the best. But it’s important to drink the entire kit as instructed. “If your colon isn’t properly cleaned out, the procedure often needs to be repeated,” Dr. Jasutkar says. 

Tip #4: Don’t ignore constipation 

When you schedule your procedure, tell your doctor if you get constipated. Patients who have chronic constipation might have a harder time with the bowel prep, says Dr. Jasutkar. In this case, your doctor may change your prep diet or prescribe other medicines. 

Tip #5: Get ahead of gas 

Sometimes patients report feeling bloated and gassy after the procedure.3 “When we do the colonoscopy, we’re pushing air or carbon dioxide into the colon to open everything up,” Dr. Jasutkar explains.   

Don’t be embarrassed to pass gas naturally. Walking can also help ease the discomfort. Or talk with your doctor about whether you can take an over-the-counter medicines to help control your symptoms, says Dr. Jasutkar. 

There’s a lot to think about when it comes to colonoscopy prep. And your Optum specialist (and their office) are there to help. You’ll get personalized care that’ll make you feel prepared and comfortable on the day of the procedure.  


  1. American Cancer Society. American Cancer Society guidelines for colorectal cancer screening. Last revised November 17, 2020. Accessed January 18, 2024. 
  2. Centers for Disease Control and Prevention. Family history of colorectal (colon) cancer. Last reviewed October 5, 2023. Accessed December 11, 2023.   
  3. Mayo Clinic. Colonoscopy. Last updated May 18, 2022. Accessed December 11, 2023. 
  4. Centers for Disease Control and Prevention. What should I know about screening?  Last updated February 23, 2023. Accessed December 11, 2023.   
  5. Mayo Clinic. Laxative (oral route). Last updated December 1, 2023. Accessed December 11, 2023. 
  6. National Institute of Diabetes and Digestive and Kidney Diseases. Colonoscopy. Last reviewed August 2023. Accessed December 11, 2023.  
  7. Mayo Clinic. Clear liquid diet. Last updated June 8, 2023. Accessed December 11, 2023.  
  8. Mayo Clinic. Sodium sulfate, magnesium sulfate, and potassium chloride (oral route). Last updated December 1, 2023. Accessed December 11, 2023.   

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