Fecal occult blood test. The CDC recommends getting a fecal occult blood test every year. This test looks for blood in the stool, one possible sign of polyps or cancer. If blood is found, follow-up tests are done.

Flexible sigmoidoscopy. In this test, a doctor uses a device called a sigmoidoscope to look at the inside of the lower third of the colon. The doctor can see polyps or remove them. The CDC recommends getting this test done once every 5 years. Often, doctors recommend flexible sigmoidoscopy in addition to annual fecal occult blood tests.

Colonoscopy. Colonoscopy is similar to sigmoidoscopy, but with colonoscopy, the doctor can look at the entire colon. It’s usually done as a follow-up test if the results of other screening tests are abnormal. For people who have no symptoms and no family or personal history of polyps, colonoscopy may be the primary screening test. In this case, colonoscopy is recommended once every 10 years.

Double-contrast barium enema. In this test, the doctor coats the colon with a substance called barium and fills it with air, then takes x-ray images. The doctor then examines the x-rays to look for polyps. Barium enemas are typically done once every 5–10 years.

Another available test is virtual colonscopy, in which the doctor inflates the colon with air and then uses computed tomography (CT) or magnetic resonance imaging (MRI) to look for polyps. Virtual colonscopy doesn't show as much detail as conventional colonoscopy, and it doesn't allow the doctor to remove polyps. If you’re over 50 and you don’t currently get regular screenings for colorectal cancer, talk to your doctor about which tests you should have and how often. For more information about colorectal cancer screening, visit the CDC’s Screen for Life Web site.