The best way to prevent colon cancer is to have a screening colonoscopy.  A colonoscopy allows your doctor to look at the colon and to remove any polyps that might turn into cancer. Colonoscopies can prevent cancer or stop it from developing. Talk with your doctor about whether a colonoscopy is the right screening test for you.

What is a Colonoscopy?

A colonoscopy is a screening test that lets your doctor see the inner lining of the large intestine (colon). The screening is not painful and can take less than an hour to do. A colonoscopy is useful, because it helps your doctor diagnose a range of colon problems that include:

  • Tumors
  • Polyps (growth that can turn into cancer)
  • Ulcers
  • Inflammation
  • Bleeding

Should I Have a Colonoscopy?

Talk with your doctor about whether a colonoscopy is the best test for you. Regular screenings are recommended for men and women starting at age 45. But some people may need to get their screenings earlier. They include:

  • African Americans
  • People who have a close relative with cancer
  • Patients with IBD, or inflammatory bowel disease
  • People with certain genetic syndromes

  • Follow your doctor's directions about when to stop eating solid foods and drink only clear liquids. You can drink water, clear juices, clear broths, flavored ice pops, and gelatin (such as Jell-O).
  • Do not eat or drink anything red or purple. This includes grape juice and grape-flavored ice pops. It also includes fruit punch and cherry gelatin.
  • Drink the "colon prep" liquid as your doctor tells you. You will want to stay home, because the liquid will make you go to the bathroom a lot. Your stools will be loose and watery. It's very important to drink all of the liquid. If you have problems drinking it, call your doctor.
  • Do not eat any solid foods after you drink the colon prep.
  • Stop drinking clear liquids for a few hours before the test. Your doctor will tell you how many hours this will be.

Learn more about preparing for a colonoscopy.


A colonoscopy may be done in a doctor's office, clinic, or a hospital.

During the test, you may get a pain medicine and a sedative put in a vein in your arm (I.V.). These medicines help you relax and feel sleepy during the test. You may not remember much about the test.

Before the test

You will need to take off most of your clothes. You will be given a gown to wear during the test.

You may lie on your left side with your knees pulled up to your belly. Because you will be given medicine during the colonoscopy, you probably won't remember having the test when you wake up.

Next, the doctor will insert a thin, flexible colonoscope in your anus and move it slowly through the rectum and into your colon. Air will be used to inflate your colon so the doctor can see the lining of the colon on a monitor.

During the test
Your doctor will look at the whole length of your colon as the scope is gently moved in and then out of your colon. You may be asked to change your position during the test.

The doctor may also collect tissue samples (biopsy) or take out growths. Usually, people don't feel anything if a biopsy is done or if polyps are taken out.

The scope is slowly pulled out of your anus, and the air escapes. Your anal area will be cleaned with tissues. If you are having cramps, passing gas may help relieve them.

After the test

After the test, you'll stay at the clinic until you wake up and then have a brief visit from your doctor. Then you'll be allowed to leave with the person who will drive you home.

How long the test takes
The test usually takes 30 to 45 minutes. But it may take longer, depending upon what is found and what is done during the test.