Skip to site content


This information does not constitute medical advice or replace discussion with your physician regarding you care or health concerns.

What is a Colonoscopy?

Colonoscopy is a procedure that uses a long, flexible, narrow tube with a light and tiny camera on one end, called a colonoscope or scope, to look inside the rectum and entire colon. Colonoscopy can show abnormalities of the lining (mucosa) of the large intestine. A gastroenterologist—a doctor who specializes in digestive diseases—performs this procedure.

Why is a colonoscopy performed?

Reasons why colonoscopy is performed include but are not limited to:

  • changes in bowel habits
  • abdominal pain
  • bleeding from the anus
  • weight loss
  • family history of colon cancer

A gastroenterologist also performs a colonoscopy as a screening test for colon cancer. Screening is testing for diseases when people have no symptoms. Screening may find diseases or their precursors at an early stage, when a health care provider has a better chance of curing or preventing the disease.

Get Screened for Colon Cancer

The American College of Gastroenterology recommends screening for colon cancer:

  • starting at age 45 for all adults
  • starting at age 40 for any person with a first degree relative with colon cancer

Medicare and private insurance companies sometimes change whether and how often they pay for cancer screening tests. People should check with their insurance company to find out how often they can get a screening colonoscopy that their insurance will cover.
Read more about colon cancer at

How does a person prepare for a colonoscopy?

Preparation for a colonoscopy includes the following steps:

  • Talk with a gastroenterologist. When people schedule a colonoscopy, they should talk with their gastroenterologist about medical conditions they have and all prescribed and over-the-counter medications, vitamins, and supplements they take, including:
  • aspirin or medications that contain aspirin
  • nonsteroidal anti-inflammatory drugs such as ibuprofen or naproxen
  • arthritis medications
  • blood thinners
  • diabetes medications
  • vitamins that contain iron or iron supplements


  • Arrange for a ride home after the procedure. Driving is not allowed until the morning after the procedure to allow time for the sedation to wear off.


  • Cleanse the bowel. The gastroenterologist will give written bowel prep instructions to follow at home. A gastroenterologist orders a bowel prep so that no stool is present inside the person’s intestine. A complete bowel prep lets the person pass stool that is clear. Stool inside the colon can prevent the gastroenterologist from clearly seeing the lining of the intestine. Instructions may include following a clear liquid diet for 1 to 3 days before the procedure and avoiding drinks that contain red or purple dye. The instructions will provide specific direction about when to start and stop the clear liquid diet.
People should call the gastroenterologist if there are additional questions about the preparation.


How is a colonoscopy performed?

A gastroenterologist performs a colonoscopy at a hospital or an outpatient center. Conscious sedation is given help people to have study with minimal or no discomfort. The medical staff will monitor people’s vital signs and try to make people as comfortable as possible. A nurse or technician places an intravenous (IV) needle in a vein in the arm to give anesthesia.

For the test, the person will lie on a table while the gastroenterologist inserts a colonoscope into the anus and slowly guides it through the colon. The scope inflates the large intestine with air to give the gastroenterologist a better view. The camera sends a video image of the intestinal lining to a computer screen, allowing the gastroenterologist to carefully examine the intestinal tissues. The gastroenterologist may move the person several times so the scope can be adjusted for better viewing. Once the scope has reached the opening to the small intestine, the gastroenterologist slowly withdraws it and examines the lining of the large intestine again.

For the test, the person will lie on a table while the gastroenterologist inserts a colonoscope into the anus and slowly guides it through the rectum and into the colon.

The gastroenterologist can remove polyps during colonoscopy and send them to a lab for testing. Polyps are potential precursors of colon cancer, so removing polyps early is an effective way to prevent cancer.

The gastroenterologist may also perform a biopsy, a procedure that involves taking a small piece of intestinal lining for examination with a microscope. The person will not feel the biopsy. A pathologist—a doctor who specializes in diagnosing diseases—will examine all the tissue that has been removed irrespective of the removal technique. Biopsy results may take a couple of weeks.

Colonoscopy usually takes 30 to 60 minutes.


What can a person expect after a colonoscopy?


  • After the colonoscopy, a person can expect the following:
  • The sedation takes time to completely wear off.
  • Full recovery is expected by the next day, and people should be able to go back to their normal diet.
  • A member of the health care team will review the discharge instructions with the person—or with an accompanying friend or family member if the person is still groggy—and provide a written copy. The person should follow all instructions given.
  • A friend or family member will need to drive the person home after the procedure.
  • If the gastroenterologist removed polyps or performed a biopsy, light bleeding from the anus is normal.

Some results from a colonoscopy are available immediately after the procedure. After the sedation has worn off, the gastroenterologist will share results with the person or a designee. Biopsy results can take a couple of days to come back and results will be mailed to the patient.

What are the risks of colonoscopy?


  • The risks of colonoscopy include but are not limited to
  • Bleeding
  • Splenic trauma
  • Perforation—a hole or tear in the the colon.
  • Infection

Bleeding and perforation are the most common complications from colonoscopy. Most cases of bleeding occur in people who have polyps removed. The gastroenterologist can treat bleeding that occurs during the colonoscopy right away. However, a person may have delayed bleeding up to 2 weeks after the test. The gastroenterologist diagnoses delayed bleeding with a repeat colonoscopy and treats it. Perforation may need to be treated with surgery.


Seek Help for Emergency Symptoms

People who have any of the following symptoms after a colonoscopy should seek immediate medical attention:

  • severe abdominal pain
  • fever
  • continued bloody bowel movements or continued bleeding from the anus
  • dizziness
  • weakness

We use cookies to make our site work. We also use cookies and other tracking technology to measure our site’s performance, personalize content and provide social media features, including through advertising and analytics partners (such as Meta/Facebook and Google). By using our site, you agree that information about your use of the site may be sent to and/or collected by these third parties, and further agree to our website Privacy Policy.