What is a colonoscopy? Are colonoscopies safe? How dangerous? Does it hurt? Can you take pills for prep? We’re here to answer your colonoscopy questions.

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Any time colorectal cancer screening comes up, the word “colonoscopy” is quick to follow. Many consider it the “gold standard” of how to get checked for colon and rectal cancer. Colonoscopy is an effective procedure with few risks.

What is a colonoscopy?

A colonoscopy is a medical procedure that allows a doctor to visually examine your entire colon and rectum. Most often, gastroenterologists (GIs) are the physicians performing the procedures.

A colonoscopy is performed using an endoscope, which is a flexible tube with a light and camera on the end, that is hooked up to a video monitor in the procedure room. The endoscope allows the doctor to get a good look at the inside of your colon and rectum.

Furthermore, the doctor can take tissue samples (biopsies) of abnormal appearing tissue and can remove potentially precancerous polyps during the same procedure.

Why is colonoscopy prep important?

Your doctor will give you detailed instructions on how they want you to prep. The prep your doctor recommends may be different from a friend’s prep or a family member’s prep.

You can be your own advocate and ask questions about colonoscopy prep options, as there are several available that vary in cost, taste, volume and timing. What’s important to consider is:

  • Cost: what can you afford? Some are over-the-counter while others require a prescription. Different insurance company formularies cover different prescriptions.
  • Taste: Some prep options taste better than others, ask your doctor what’s been most tolerable yet also effective. You can also ask your doctor about eating certain foods the day before your colonoscopy , as it may be permitted in some case.
  • Volume and timing: There are some low-volume prep options, preps in pill-form, and also split-dose options based on the time of day you’re scheduled for a colonoscopy.

Whichever prep you and your doctor land on, make sure you follow your doctor’s instructions. The last thing you want is an incomplete prep that leads to your doctor either missing something or requesting you redo the prep and reschedule your procedure.

Don’t assume you are “empty enough and have nothing left in you” and stop the prep early. Remember, even though you are not eating, your body still makes waste material that needs to be flushed out.

It’s a good idea to read through the directions before the day of prep so that if you have any questions, you’re not stuck if you’re unable to get in touch with someone from your doctor’s office.

When you complete the prep as directed, you give your GI the cleanest and clearest visual into all areas of your colon and rectum, which will result in a thorough colonoscopy.

Read our blog for more colonoscopy prep tips from patients.

Talking to your GI

Another really important part to preparing for your colonoscopy is making sure the GI team knows about your current medical issues, allergies, and prescribed medications well before your procedure date. This includes over-the-counter medications and your social habits that may affect the sedative plan (such as alcohol consumption, cannabis consumption, etc.)

This information helps them ensure you are getting the right sedation/anesthesia. They will also give you detailed instructions about whether you need to adjust any of your medications, such as diabetes medications or blood thinners.

Please also mention if you have had a colonoscopy in the past and if you had any issues with the bowel prep or the sedation. This information is really helpful to ensure a successful procedure.


What happens during a colonoscopy?

Most colonoscopies are performed at procedure centers or hospitals. It’s considered an outpatient procedure, so don’t expect to stay overnight. You will need to line up transportation since the procedure involves sedation and you won’t be able to drive yourself home.

After checking in, you’ll be directed to an area where you will change into a hospital gown (opening goes toward the back!).

Advice: Don’t take valuables like rings or cash—leave as much at home as possible.

Once you’re changed, you’ll get into a hospital bed, and nurses and techs will take your vital signs and start an IV for you. This will help keep you hydrated, and it’s also how any medications, including sedation, will be given.

Don’t worry if you need to use the restroom: They understand! Just ask.

You’ll likely meet with several people before going into the procedure room: nurses, doctors, and your anesthesiologist. They’ll ask you questions about your health history, if you’re seeing any signs or symptoms, or if you have any concerns. Your anesthesiologist will make sure you haven’t had anything to eat or drink since the time they asked you to stop in your prep instructions.

Tell the truth, so the colonoscopy can be safely performed.

When it’s time for your procedure, your medical team will wheel your bed into the exam room. Typically, you’ll get an oxygen tube under your nose and be asked to roll over to your left side.

As the sedative goes in, the room will get fuzzy, and you’ll feel sleepy. Most of the time, the next thing you remember is being in the recovery area.

What happened while you slept?

While you slept, the doctor did a rectal exam and then used the long, thin endoscope to get a good look at your colon and rectum. He or she carefully guided the scope to look through all of the folds and crevices of your large intestine, starting at the rectum and going to where your large intestine meets your small intestine.

If they found a colon or rectal polyp, they removed it and sent off the biopsy to a pathology lab for testing. If there was bleeding, they may have cauterized it (sealed off the bleeding by burning it) or clipped it (put a small metal clip over the site, which will fall off on its own) – don’t worry, this doesn’t hurt.

The endoscope allows the GI to take photos of your colon, and what they found. You should receive a printout with those pictures before you head home. Your health care team will make sure your vitals look OK, you can get dressed, you’re coherent, and you have transportation to get you home before you’re discharged.

How long does a colonoscopy take?

On average, a colonoscopy procedure takes 15 to 45 minutes; however, ask your doctor’s office how much time you can expect getting a colonoscopy to take. They will help you estimate total time for check-in, pre-procedure, procedure, and recovery.

How long is recovery?

You’ll be in a recovery area as you stay at the hospital or outpatient center for at least 30 minutes, but you should also plan to take the rest of the day off once you’re discharged. You won’t be permitted to drive home or even for the rest of the day. In the majority of cases, you can return to your normal diet.

Take it easy the day of your colonoscopy. Especially after your colonoscopy.

You may feel 100% better, but the sedation remains in your system for hours after your procedure. So don’t plan to drive, work, make important decisions, or drink alcohol following your procedure.

Is colonoscopy safe or dangerous? What are the risks? 

Colonoscopy is a safe procedure. Thousands are performed each day. Most patients have little to no complications with them, and they return to routine activities by the following morning. Be sure to talk with your medical team if you’re taking medications and supplements (particularly medicines that thin the blood), or if you use other medical devices.

The medical office will let you know what to bring and if you need to stop taking certain medications prior to getting a colonoscopy. This may require coordination with your prescribing doctor (primary care, cardiology, neurology, etc.).

Every medical procedure comes with risks, however. It’s important to discuss these with your doctor before having a colonoscopy. Although rare, some of these complications from colonoscopy can occur, and you need to contact your doctor right away:

  • Dehydration
  • Bleeding 
  • Infection 
  • Bowel perforation
  • Bad reaction to anesthesia 
  • Blood clotting

Not getting screened for colorectal cancer puts you at the greatest risk. However, if you cannot undergo a colonoscopy, you may have other screening options.

If you have a family risk of colorectal cancer, or if you have signs and symptoms, you will need to have a colonoscopy because alternate screening options are not sufficient to exclude cancer for patients at increased risk based on family history or symptoms.

Is colonoscopy painful?

Typically, no. The majority of patients who have a colonoscopy say the most challenging part is the prep (and in the grand scheme of things, it really isn’t that bad). That’s why colonoscopy planning is important.

The procedure itself is not painful. You may feel slight discomfort and pressure as the doctor inserts the scope, but that is uncommon. If you do experience this, it is short lived.

Because gas is pumped into the colon to inflate it so doctors can get a good look, gas and bloating are also common following a colonoscopy. However, as the day goes on, the air will exit.

What’s the colonoscopy age?

Everyone who is considered average-risk for colorectal cancer needs to begin screening at age 45. If you have a family history of colorectal cancer or high-risk precancerous polyps, or you see signs and symptoms, you may need to be screened sooner. If this is your case, you’ll need a colonoscopy, not another screening method.


I hear colonoscopy prep is awful: Is that true?

It can be! However, a lot of improvements have been made to colonoscopy prep over the years.

There are FDA-approved pills/tablets, drinks, and enemas for colonoscopy prep. Your doctor will likely have a preferred method of prep (and accompanying instructions). But, your doctor also has several options you can choose from.

Some options are over-the-counter, others require prescriptions. Some taste better than others.

The best quality preps include where you take some at night and some in the morning (split-dose prep). There are also preps where the amount of laxative you drink is far less compared to other options (low-volume bowel prep).

Some doctors allow patients to eat a low-residue diet in combination with over-the-counter laxatives the day before. Some insist on prescription preps because they are far superior when it comes to cleaning out the colon and getting a good view. It really depends on what you and your doctor agree on what’s best.

If you’re unsure about what’s best for you, ask your doctor for options or ask other patients. Choose the prep that’s best for you. And, if you get to prep night and cannot complete the prescribed prep, call your doctor right away.

A completed prep is most important, and they can offer you another option to get you fully cleaned out.

Are there pills to take for colonoscopy prep?

Yes, there are liquid solutions as well as prep pills that can be used for colonoscopy prep. The most common ones include:

Liquid solutions

  • MoviPrep®
  • MiraLAX®® with Gatorade®
  • TriLyte®

Prep pills/tablets

  • OsmoPrep®
  • SUTAB®

The Cleveland Clinic unpacks the pros and cons of each bowel prep option. 

If your doctor is unable to complete the colonoscopy due to a technical issue, they may recommend a specialized CT scan that can visualize the colon (CT colonography).

How often will I need a colonoscopy?

Your frequency will depend on a few things:


If you’re at average risk of colorectal cancer, you don’t have any symptoms, you had a clean colonoscopy and no concerns, you’ll likely be encouraged to repeat the procedure in 10 years.

Colonoscopy Findings

If a doctor found and removed a possibly precancerous colon or rectal polyp or saw any other areas of concern, you will likely be encouraged to repeat the colonoscopy sooner than 10 years; depending on the number, size, and histology of polyps (what they look like under the microscope). This may be in one, three, five, or seven years. 

Your symptoms

If you’re seeing blood in the stool, experiencing constipation or diarrhea, facing unexplained weight loss, or having other symptoms of colorectal cancer, you need to talk with your doctor. A colonoscopy may be recommended.

Your personal risk

If you have a history of colorectal cancer or advanced precancerous colorectal polyps, both personally and/or within your family, you will need to undergo colonoscopy earlier than the general population and more frequently.

Are you at risk? Take our 1-minute Colorectal Cancer Screening Quiz.

Depending on who in your biological family was diagnosed with cancer/advanced polyps and at what age, you may need to get a colonoscopy every three to five years.

If you have an immediate biological family member who has had colorectal cancer or advanced colorectal polyps (mom, dad, sibling), it’s recommended that you begin screening for colorectal cancer when your age is 10 years younger than when they were diagnosed. So, for example, if your mom was diagnosed with colorectal cancer at age 45, your screening should begin at age 35.

Are colonoscopies worth the risk? 

Only you can make the decision to get a colonoscopy. It’s generally a safe procedure, and it’s a popular option for colorectal cancer screening because your doctor can both find and remove polyps in one session.

At-home screening tests are also an option if you’re not ready for a colonoscopy, but you need to get your screening done and repeat it regularly (at-home tests must be done every one to three years, depending on the type of test). However, if your test shows any abnormalities, to complete the screening process, a follow-up colonoscopy will need to be performed to determine why the at-home test was abnormal.

Whenever considering colonoscopy, a discussion with your doctor is important. While the procedure is the same for everyone, how you prep, when you need one, and how often you need one will be unique for you.

But remember: The greatest risk is not getting screened at all.


Has Fight CRC taken action for colonoscopies?

Yes! We are proud to say that decades of advocacy and research have led to these changes for colonoscopy in the U.S.:

Fight CRC has a long history of fighting for colonoscopy coverage, especially among Medicare patients. We will continue to fight until everyone has equal and fair access.

Does Medicare cover a colonoscopy?

Yes. BUT only screening colonoscopies have no out-of-pocket expenses. Medicare Part B must cover the full cost of a screening colonoscopy per ACA guidelines. That means only colonoscopies done to prevent rather than diagnose or treat colorectal cancer. 

Please note: If a polyp or other tissue is removed, you may be responsible for part of the cost and billed a co-insurance because the colonoscopy is now diagnostic. How often Medicare covers the procedure depends on your health and risk factors. 

For average-risk individuals, a screening colonoscopy is covered every 10 years and for high risk individuals it is covered every two years. 

**The cost sharing for polyp/abnormal tissue removal is slowly being phased out over eight years as a result of the Removing Barriers to Colorectal Cancer Screening Act of 2020. Learn more about if Medicare covers a colonoscopy by AARP and on the colonoscopy coverage website.

Is colorectal cancer included in the Affordable Care Act cancer screening?

YES, BUT grandfathered health plans are excluded.

The Affordable Care Act (ACA) requires both private insurers and Medicare to cover the costs of colorectal cancer screening tests. The law states that there should be no out-of-pocket costs for patients that receive a screening test assigned an A or B rating by the United States Preventive Services Task Force (USPSTF). 

However, this rule does not apply to grandfathered health plans that were in place prior to the ACA. Call your insurance company to find out if you have a grandfathered plan. 

Medical Review

Swati Patel
Swati Patel, MD, MS

University of Colorado Anschutz Medical Campus

Last Reviewed: January 12, 2024