How to Prepare for a Colonoscopy

A colonoscopy — and the steps required to get one — can cause a spike of anxiety, but don’t worry. Understanding the health benefits and the correct way to prepare for this routine procedure can assuage any apprehension.

Plus, if you have an upcoming colonoscopy, you’re in good company. More than 15 million people in the U.S. undergo one every year, according to a 2023 review in the journal Translational Gastroenterology and Hepatology.

What Is a Colonoscopy?

A colonoscopy is an invasive procedure in which a physician places a long, flexible tube outfitted with a small video camera into the rectum. The camera allows the doctor to view the entire colon and search for abnormalities or changes that could be warning signs for colorectal cancer.

There are lots of opportunities to check for abnormalities during a colonoscopy, says Dr. Prasun Shah, a gastroenterologist with Memorial Hermann in The Woodlands, Texas. This includes:

— A full rectal exam, including of the anal sphincter tone, prostate and perineal area.

— Inflammatory changes throughout the entirety of the colon, like signs of Crohn’s disease.

— Conditions of nearby organs, such as the appendix.

— Polyps or precancerous growths, which are removed during the procedure. “If we find a suspicious tumor which cannot be removed via colonoscope, then we tattoo that area with ink so it can be identified easily for any future surgical interventions,” Shah adds.

Colorectal cancer, according to the American Cancer Society, is the third most common cancer (excluding skin cancers) and, for both men and women, the third leading cause of cancer-related death. Lifestyle factors, such as diet and exercise, as well as family history of the condition, are major risk factors for colorectal cancer. For this reason, colorectal cancer is still prevalent in younger populations. The risk of a colorectal cancer diagnosis increases significantly with age. ACS reports that diagnosis rates increase more than 80% every five years until the age of 50, and then more than 20% after age 55.

However, overall colorectal cancer rates have been steadily dropping, thanks to screenings like colonoscopies.

[SEE: Colon Cancer Symptoms That Are Easily Overlooked.]

Will I Get Anesthesia for a Colonoscopy?

To prepare for your colonoscopy, understand which anesthesia options are available to you.

This may include:

No sedation. According to the American Society of Anesthesiologists, only 2% of colonoscopies are performed without any sedation. Individuals may opt for a no-sedation option due to cost or personal choice, like wanting to drive home after the procedure.

Minimal or light sedation. Your doctor may give you pain medications, like fentanyl, to help you relax, but you’ll be awake.

Moderate sedation. Your health care provider will give you higher doses of pain medications, so it’s likely you’ll be drowsy and won’t remember the procedure.

Deep sedation. Your provider will give you an anesthesia medication like propofol, which makes you unconscious.

General anesthesia. This type of anesthesia puts you completely “under,” so you would be on a ventilator during the procedure. This is less common for colonoscopies.

Deep sedation with propofol is a common and effective method for anesthesia during a colonoscopy.

“Whenever possible, providers are willing to work with patients who request propofol. It is preferred by most patients and providers because the sedation is more effective as well as more efficient due to propofol’s speed of onset and ability to rapidly diminish when stopped,” says Dr. Aurora Quaye, a member of the ASA and anesthesiologist at Maine Medical Center in Portland.

Quaye was also a lead author in a 2024 study published in Anesthesiology, the peer-reviewed journal of the ASA, concluding that deep sedation with propofol is correlated with increased detection of serrated polyps, which are often missed. Serrated polyps are precancerous, but they’re ultimately responsible for around 20% of colorectal tumors.

Will Insurance Cover My Colonoscopy?

Most insurance policies cover a screening colonoscopy for an average-risk patient every 10 years beginning at age 45, says Dr. Lauren Bleich, a gastroenterologist with Gastro Health in Acton, Massachusetts. Most plans will also cover this preventive service if you have specific risk factors, like family history of colorectal cancer or certain genetic conditions.

Some health insurance plans may require prior authorization. Common reasons for insurance denials may include:

— Your insurance thinks you are getting the procedure too frequently.

— You’re younger than screening recommendations and have no risk factors.

— Your submitted health history was incomplete.

— You are getting the procedure for a diagnosis rather than a screening, which may follow a separate insurance claim process.

Bleich encourages you to share all of your medical information with your physician, so that documentation can be complete.

“This information will be shared with your insurance company to facilitate coverage of costs,” she adds.

How to Prepare for a Colonoscopy

Adequate bowel preparation is key for an effective colonoscopy, says Dr. Paul Johnson, a colon and rectal surgeon at Methodist Le Bonheur Healthcare in Memphis, Tennessee. Proper prep increases the physician’s ability to detect small or flat polyps and decreases the rate at which they might miss polyps.

“In short, poor bowel prep means repeat colonoscopy,” Johnson explains.

The steps you need to take to prepare for a colonoscopy include:

— Cut down on your consumption of high-fiber foods three days before the procedure.

— Consume a clear liquid diet the day before the colonoscopy.

— Drink prescription bowel-cleaning liquid the morning of and the evening before the procedure.

— Arrange to have a responsible driver take you home after the procedure.

1. Cut down on your consumption of high-fiber foods three days before the procedure.

Fiber residue, even small particles, can be harder to remove through suction during the colonoscopy. A low-residue diet beginning three days before the procedure is a common standard so your physician has a clear view of your colon.

High-fiber foods include:

— Beans

Seeds (including flax, sunflower and quinoa)


— Multigrain bread

Fresh or dried fruit

— Popcorn

— Salads

— Vegetables

[See: Colon Cancer Diet.]

2. Consume a clear liquid diet the day before the colonoscopy

A clear liquid diet often includes:

— Gelatin

— Clear soup

— Clear juices



— Coffee without cream or milk

3. Drink bowel-cleaning liquid the morning of and the evening before the procedure

Bowel-cleansing liquid acts as a laxative to clear your colon, thus making it easier to detect any polyps. The recommendations are to:

— Consume the first half of the bowel preparation the night before the colonoscopy and the second half about four hours before a morning colonoscopy.

— For an afternoon colonoscopy, drink all of the bowel preparation in the early morning on the day of the colonoscopy.

— Don’t allow more than four to six hours between the ingestion of the last dose of the bowel-cleansing preparation prep and the start of the colonoscopy.

Consuming the bowel-cleansing liquid in a split dose results in “decreased intensity and duration of (bowel movements), less patient inconvenience, improved bowel preparation and increased … polyp detection rates,” according to research published in 2016 in the American Journal of Gastroenterology. Burke is one of the study’s co-authors.

Burke notes that once-stigmatized bowel preparations have improved because:

— The taste of the prescription bowel preparation liquids is more palatable.

— Liquid bowel-cleansing formulas are more efficient than they used to be, so you don’t have to drink nearly as much as you did in the past.

— Different bowel preparation options are available, including lower-volume preps — 3-liter, 2-liter and 10-ounce bowel doses, or even preparation tablets for some patients.

Ask your physician about the best bowel preparation options for you.

4. Arrange to have a responsible driver take you home after the procedure

A colonoscopy requires sedation, so medical offices will typically require you to have a responsible person — a friend or a relative — drive you home after the procedure once you’re discharged.

If you don’t have someone to drive you home, discuss your concerns with facility who scheduled your procedure. They may be able to connect you with a local medical transport service or assist you if you have Medicaid or insurance benefits that cover transportation.

[READ: Everything You Need to Know About Colorectal Surgery.]

Emerging Research

Since colon cancer is the third most commonly diagnosed cancer, researchers continue to study how to make screening more efficient and effective.

Is a special diet before a colonoscopy necessary?

A review of 13 studies compared those who prepared with a low-residue diet, which avoids fibrous foods like whole grains, nuts and seeds, to those who prepared with a clear liquid diet. The study determined that the low-residue diet had no adverse effects.

Another 2024 study published in Endoscopy scrutinized whether any dietary restrictions before a colonoscopy are necessary. The study, which followed a little over 500 subjects, compared those who prepared with no dietary restrictions versus those who prepared with a one-day low-residue diet. The study concluded the group with no dietary restrictions had equally efficient procedures but that more research is needed.

Additional research may lead to a change in the standard of care for colonoscopies. If a more flexible diet makes the procedure easier to tolerate and makes people less likely to cancel it, colonoscopy prep may become a thing of the past.

Do colonoscopies reduce cancer risk?

Colonoscopies are largely considered the gold standard of colorectal cancer screenings. A 2022 New England Journal of Medicine study of about 85,000 people, however, has drawn attention in the world of cancer. This study suggests that colonoscopy screenings led to just an 18% reduction in colorectal cancer and no significant decrease in death.

However, both Burke and Johnson point out caveats:

— First, only 42% of participants underwent a colonoscopy; when additional analysis considered if all participants had undergone a colonoscopy, the results showed a 31% reduction in the risk of colorectal cancer and a 50% reduction in deaths.

— Second, this study was performed in Norway, Poland and Sweden. In the U.S., American Indian, Alaska Native and Black Americans are more likely to have colorectal cancer and more likely to die from it, compared with their white counterparts.

— Finally, it’s essential for physicians to stay in touch with their patients through follow-up appointments. This way, they can keep an eye out for any new polyps. The study didn’t include follow-up guidelines or data on whether participants and physicians were tracking polyp growths.

In general, colonoscopies are still one of the best ways to suss out colorectal cancer. So, if you’re at least 50 years old, according to U.S. Preventive Services Task Force guidelines — or earlier if you’re average- to high-risk — it’s a good idea to make that appointment.

More from U.S. News

Preparing for Your First Cancer Appointment: Questions to Ask Your Oncologist

Colon Cancer Diet: Foods to Eat to Lower Your Risk

Questions to Ask Your Doctor About Prostate Cancer

How to Prepare for a Colonoscopy originally appeared on

Update 05/09/24: This story was previously published on an earlier date and has been updated with new information.

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