A colonoscopy is considered the gold standard when it comes to screening for colon polyps and colorectal cancer. Yet 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. While people often dread the prep involved for a colonoscopy, the screening saves lives. Read more to learn how to best prepare for this procedure, how much time it will take and other important information you should know about colonoscopies.
[Read: Do Home Cancer Tests Work as Well as a Colonoscopy?]
What Is a Colonoscopy?
A colonoscopy is an outpatient procedure performed at a hospital or an ambulatory surgery center. During a colonoscopy, patients are put under sedation. 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.
The procedure itself is painless, but the prep is often considered challenging. The goal is to empty your bowels so your gastroenterologist can properly examine the inside of your colon. If there’s still stool in your colon, your doctor may not be able to see polyps or other problems and you may need to have the procedure again.
An actual colonoscopy typically takes between 15 and 60 minutes. The length will depend on if any abnormalities are found and other factors. However, the entire process may take 2 to 3 hours, including preparation and recovery time.
There are lots of opportunities to check for abnormalities during a colonoscopy, notes 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
[SEE: Why Are More Young Adults Getting Colon Cancer?]
Why a Colonoscopy Is Important
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. The 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.
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.
[SEE: Procedures Commonly Performed at Ambulatory Surgery Centers]
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:
1. Cut down on your consumption of high-fiber foods three days before the procedure.
2. Consume a clear liquid diet the day before the colonoscopy.
3. Drink prescription bowel-cleaning liquid the morning of and the evening before the procedure.
4. 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)
— Nuts
— Multigrain bread
— Popcorn
— Salads
— Vegetables
2. Consume a clear liquid diet the day before the colonoscopy
A clear liquid diet often includes:
— Gelatin
— Clear soup
— Clear juices
— Water
— Tea
— 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, the timing of your bowel prep may be shifted.
— Always be sure to follow your doctor’s instructions for bowel prep. If you have questions, reach out to the office.
— 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 the American Journal of Gastroenterology.
Dr. Carol Burke, a gastroenterologist at the Cleveland Clinic in Ohio and one of the study’s coauthors, 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.
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.
[READ: Everything You Need to Know About Colorectal Surgery.]
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.
Bottom Line
Colonoscopies are largely considered the gold standard of colorectal cancer screenings and are still one of the best ways to suss out colorectal cancer. So, if you’re at least 45 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.
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How to Best Prepare for a Colonoscopy originally appeared on usnews.com
Update 03/04/25: This story was previously published on an earlier date and has been updated with new information.
