Know Before You Go: Colonoscopy

Get tips for what you should do to prepare for a colonoscopy, and learn what to expect during and after your procedure from Dr. Oz.

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Colonoscopies can find cancer and save lives, plain and simple. Although you may not look forward to this procedure, it is a relatively easy and effective way to catch colon cancer before it catches you. Alleviate your concerns and eliminate confusion by knowing what to expect before, during and after your colonoscopy.

This content originally appeared on

Medically reviewed in June 2019.

Who Needs a Colonoscopy

2 / 7 Who Needs a Colonoscopy

Men and women at average risk should begin colon cancer screening at age 45 or 50—guidelines disagree, so talk to your doctor—using colonoscopy or another test, and continuing (at least) until age 75. The frequency depends on which test you choose and what your doctor finds during the screening.

People with either a first-degree relative who was diagnosed with colon cancer or adenomatous polyps before the age of 60, or two first-degree relatives diagnosed at any age should be screened starting at age 40 or 10 years before their relative was diagnosed, whichever is earlier. Some people with diseases that predispose them to cancer, such as ulcerative colitishereditary nonpolyposis colon cancer (HNPCC) or familial adenomatous polyposis (FAP), may require colonoscopies earlier.

Before the Colonoscopy

3 / 7 Before the Colonoscopy

Starting a day before your procedure, you should stop eating solid foods and only have clear liquids, including water, broths, tea, black coffee, clear juices and Jell-O. A good general rule is that if you can read the newspaper through it, it’s a clear liquid. Avoid anything with red, blue or purple coloring. Your doctor may also want you to temporarily stop taking or change the doses of certain medications prior to the procedure (such as blood thinners), so be sure to check with him or her ahead of time. Rarely, your doctor may ask you to take an antibiotic beforehand.

Tips for Prepping

4 / 7 Tips for Prepping

In order for the doctor to get a clear view of your colon, you will need to complete a bowel prep before your colonoscopy. The type of bowel prep varies depending on your doctor, so be sure to ask what kinds are offered, as you may have a choice. You may also be asked to combine different forms of bowel prep. The bowel prep will usually start the day before your procedure, but your doctor will give you explicit instructions about when and how to prepare.

Know Your Options

5 / 7 Know Your Options

The different types of bowel prep include pre-prepared laxative solutions or laxatives that you mix in with electrolyte solutions or sports drinks, a laxative pill that you will take along with plenty of fluids to keep from getting dehydrated or disrupting your electrolytes or an enema that uses water to wash out your colon. Be sure to complete the entire prep per the instructions—if you don’t, your doctor may not be able to see your entire colon and may have to repeat the colonoscopy. You should make sure you have easy and fast access to a toilet after you start the prep, as it will cause diarrhea.

During the Colonoscopy

6 / 7 During the Colonoscopy

You will likely be given sedation and anesthesia to ease discomfort during the procedure, and most people do not remember very much (if anything) afterwards. The doctor will use a long flexible tube with a camera on the end to search for any concerning polyps that may represent cancer.

If your doctor is worried about any areas within your colon, he or she will take a biopsy and send it to be examined by a pathologist. Some precancerous or early cancerous polyps may actually be completely removed during the colonoscopy. Expect the procedure itself to last about 20-60 minutes, but the entire process from arrival to departure usually takes several hours and may last as long as five hours.

After the Colonoscopy

7 / 7 After the Colonoscopy

After the procedure, you will rest for about 30 to 60 minutes while the sedation wears off. Because of the medication you received during the procedure, you will be drowsy and should not drive, so make sure you have a ride home. You should not drive or work for the rest of the day.

Discomfort after the procedure should be minimal, but may include mild cramping, bloating or flatulence. It’s possible that you will notice a small amount of blood in your first bowel movement after a colonoscopy, especially if your doctor removed a polyp. If you have large amounts of blood in your stool or you continue to pass blood, or if you have persistent abdominal pain or fever over 100° F, call your doctor.

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