Colonoscopy Fact Sheet

Learn how to prepare and what to expect during this procedure.

What is a colonoscopy?

A colonoscopy can be used as both a screening test (meaning it is done in healthy, asymptomatic patients) and as a test to evaluate for a specific diagnosis.  During a colonoscopy, a doctor will use a scope to look inside your rectum and colon for irritated and swollen tissue, ulcers, polyps, and cancer. A colonoscopy allows doctors to both evaluate or diagnose gastrointestinal disorders, like diverticulosis and inflammatory bowel disease, and provide treatment for certain conditions in one examination.

At what age should you get your first colonoscopy?

Most people can begin getting their first colonoscopy at age 50.  However, if you have a personal or family history of colorectal cancer, a personal history of inflammatory bowel disease, certain hereditary diseases, or a personal history of radiation exposure, your doctor may recommend you start at age 45.  Depending on the findings, this test can then be performed every five or 10 years to screen for colon and rectal cancer. Screening is recommended until age 76 and becomes an option from then through age 85.

What does your doctor check during the exam? 

During a colonoscopy, your doctor will check your entire colon and rectum for inflamed tissue, abnormal growths like polyps, ulcers, and early signs of cancer. If you have symptoms like bleeding from the anus, changes in your bowel activity like diarrhea, pain in your abdomen, or unexplained weight loss, a colonoscopy may help your doctor find the cause.

How do you prepare for the procedure?

In the days leading up to a colonoscopy, your doctor will send you written instructions to prepare your bowels and ensure there is little to no stool remaining in your intestine at the time of the procedure, which will make it easier for your doctor to see your lining clearly.

The bowel prep kit varies depending on the patient’s needs and the doctor, but they typically contain various laxatives in the form of pills, dissolvable powders, or clear liquids. One of the most common methods of clearing the colon involves drinking a polyethylene glycol solution, which will cause extreme diarrhea the evening before the procedure and five hours before coming in for the test. Your doctor may also prescribe a laxative pill to take before going to bed in addition to the polyethylene glycol solution.

For one to three days before a colonoscopy, you may be asked to follow a liquid diet and avoid red and purple-colored drinks. Bouillon, broth, lemon, lime or orange gelatin, plain coffee or tea, sports drinks, strained fruit juice like apple or white grape, and water will likely make up your diet during the preparation period.

For a more detailed explanation of the preparation process, check out these instructions from Dr. Oz’s own gastroenterologist, Dr. Jonathan LaPook.

What should you expect when getting a colonoscopy? 

The 30-60 minute procedure will take place in a hospital or outpatient facility and will likely include “intravenous sedation” or “twilight sedation,” which will make you very drowsy but capable of breathing on your own.

Once you’re sedated and lying on your side, your doctor will insert a scope equipped with a tiny camera through your anus and into your rectum and colon. The scope will inflate your large intestine with air, allowing your doctor to view it on a video monitor. Once the scope reaches your small intestine, your doctor will slowly pull it back and re-examine your large intestine.

While examining your colon, your doctor may also remove polyps, which are precancerous lesions.  The doctor may also retrieve a biopsy of abnormal tissue to be sent to a lab for testing. Luckily, you won’t feel any of these removals, and you likely won’t even remember the procedure.

Are there any side effects? 

Within the first hour following the procedure, you may feel cramping in your abdomen or bloating, and you won’t be able to drive yourself home from the facility. By the next day, you can get back to your normal diet. If you’ve had a biopsy or polyps removed, you may experience normal light bleeding from your anus.


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