A colonoscopy is an examination of the bowels using a colonoscope, or a thin, flexible tube with a light and camera. It can help identify issues like colorectal cancer, polyps, and ulcers.

During a colonoscopy, your doctor checks for abnormalities or disease in your large intestine, particularly the colon. They’ll use a colonoscope, a thin, flexible tube that has a light and camera attached.

The colon helps form the lowest portion of the gastrointestinal tract. It takes in food, absorbs nutrients, and disposes of waste.

The colon is attached to the anus via the rectum. The anus is the opening in your body where feces are expelled.

During a colonoscopy, your doctor may also take tissue samples for biopsy or remove abnormal tissue such as polyps.

A colonoscopy can be performed as a screening for colorectal cancer and other problems. The screening can help your doctor:

The American College of Surgeons estimates that 90 percent of polyps or tumors can be detected through colonoscopy screenings.

The American College of Physicians recommends a colonoscopy once every 10 years for people who meet all the following criteria:

  • are 50 to 75 years old
  • are at average risk of colorectal cancer
  • have a life expectancy of at least 10 years

The British Medicine Journal (BMJ) recommends a one-time colonoscopy for people who meet all of these criteria:

  • are 50 to 79 years old
  • are at average risk of colorectal cancer
  • have at least a 3-percent chance of developing colorectal cancer in 15 years

The American Cancer Society (ACS) and the U.S. Preventive Services Task Force recommend beginning screen at 45 years old, so speak with your doctor to determine when you should start screenings based on your needs.

If you’re at an increased risk for colorectal cancer, you may need more frequent procedures. According to the ACS, people who may need to be screened as often as every 1 to 5 years include:

  • people who’ve had polyps removed during a previous colonoscopy
  • people with a prior history of colorectal cancer
  • people with a family history of colorectal cancer
  • people with inflammatory bowel disease (IBD)

Since a colonoscopy is a routine procedure, there are typically few lasting effects from this test. In the vast majority of cases, the benefits of detecting problems and beginning treatment far outweigh the risks of complications from a colonoscopy.

However, some rare complications include:

  • bleeding from a biopsy site if a biopsy was done
  • a negative reaction to the sedative being used
  • a perforation in the rectal wall or colon

A procedure called virtual colonoscopy uses CT scans or MRIs to take pictures of your colon. If it is an option and you opt for it instead, you can avoid some of the complications associated with traditional colonoscopy, although bowel prep is still required.

However, it comes with its own disadvantages. For instance, it has slightly less sensitivity in seeing very small polyps when compared to traditional colonoscopies. As a newer technology, it’s also less likely to be covered by health insurance.

Bowel prep for a colonoscopy

Your doctor will give you instructions for bowel preparation (bowel prep). You must have a clear liquid diet for 24 to 72 hours before your procedure.

The typical bowel prep diet includes:

  • broth or bouillon
  • gelatin
  • plain coffee or tea
  • pulp-free juice
  • sports drinks, such as Gatorade

Make sure not to drink any liquids containing red or purple dye because they can discolor your colon.


Tell your doctor about any medications you’re taking, including over-the-counter drugs or supplements. If they can affect your colonoscopy, your doctor may tell you to stop taking them. These might include:

Your doctor may give you a laxative to take the night before your appointment. An enema may also be recommended in certain cases, to flush out your colon on the day of the procedure.

You may want to arrange for a ride home after your appointment. The sedative you’ll be given for the procedure makes it unsafe for you to drive yourself.

How to prepare for a colonoscopy if you’re pregnant

A colonoscopy during pregnancy is typically recommended only when necessary but is relatively safe for both the pregnant parent and the baby. If it’s only for a regular screening, your doctor may ask you to wait until after you’ve given birth.

Since nutrition is so important during pregnancy, you’ll want to speak with your doctor about how to bowel prep beforehand and what types of laxatives, if any, will be necessary and safe to take.

  • Just before your colonoscopy, you’ll change into a hospital gown. Most people have sedation and pain medication. Typically, this is in the form of monitored anesthesia, but lower levels of sedation may also be available upon request and in consultation with your doctor.
  • During the procedure, you’ll lie on your side on a padded examination table. Your doctor may position you with your knees close to your chest to get a better angle to your colon.
  • While you’re on your side and sedated, your doctor will guide the colonoscope slowly and gently into your anus through the rectum and into the colon. A camera on the end of the colonoscope transmits images to a monitor that your doctor will be watching.
  • Once the colonoscope is positioned, your doctor will inflate your colon using carbon dioxide. This gives them a better view.
  • Your doctor may remove polyps or a tissue sample for biopsy during this procedure.
  • The entire procedure takes 15 minutes to an hour.

After the procedure is done, you’ll wait for about an hour to allow the sedative to wear off. You’ll be advised not to drive for the next 24 hours, until its full effects fade.

If your doctor removes tissue or a polyp during a biopsy, they’ll send it to a laboratory for testing. Your doctor will tell you the results when they’re ready, which is normally within a few days.

Colonoscopy results

Here are some of the results you may receive after a colonoscopy:

  • Normal findings or negative results: No abnormalities were discovered. If you have average risk of colorectal cancer, your doctor will likely suggest having the next screening in 10 years.
  • Colonic polyps: A growth of tissue in the colon lining. These can either be benign (noncancerous) or neoplastic (cancerous or precancerous). Smaller polyps can often be removed during the procedure, though larger ones may require surgical intervention. A history of polyps may require more frequent screenings.
  • Other potential results: such as diverticular disease (small sacs pushed out against the colon lining), hemorrhoids (swollen veins around the anus or in the rectum), inflammation, or fistulas (abnormal openings in your digestive tract).

You’ll likely have some gas and bloating from the gas your doctor placed into your colon. Give this time to get out of your system. If it continues for days after, it could mean there’s a problem and you should contact your doctor.

Also, a little bit of blood in your stool after the procedure is normal. However, call your doctor if you:

How long does a colonoscopy take?

A typical colonoscopy takes about 15 minutes to an hour, depending on whether the doctor has to remove any polyps or tissue for a biopsy. Plan to spend a few hours at the hospital or endoscopy clinic in total to account for preparation and recovery from the sedative.

Are colonoscopies painful?

Colonoscopies are not typically painful since the sedative will prevent you from remembering the procedure. If you aren’t in the United States, speak with your doctor about what options are available for pain management if a sedative isn’t an option. There could be some mild discomfort in the rectum or stomach after the procedure as well as some bloating from the carbon dioxide.

At what age should I start getting colonoscopies?

Some organizations have recommended colonoscopy screenings every 10 years between ages 50 and 75 years if they are at average risk for colorectal cancer. However, some organizations have recommended starting screenings at 45 years old instead.

Speak with your doctor about your circumstances to determine when to start screenings.