But when should you start?

People who have no identified risk factors – other than age -- should begin testing for colon cancer at age 50. If you have a family history of this cancer or have other conditions such as inflammatory bowel disease, you should talk with your doctor about starting earlier.

There are several different tests that can find colorectal cancer. The American Cancer Society recommends that people at average risk use one of the screening tests below:

• flexible sigmoidoscopy every 5 years* 
• colonoscopy every 10 years 
• double contrast barium enema every 5 years* 
• CT colonography (virtual colonoscopy) every 5 years*

Tests that mainly find cancer

• fecal occult blood test (FOBT) every year*,**
• fecal immunochemical test (FIT) every year*,**
• stool DNA test (sDNA), interval uncertain*

*Colonoscopy should be done if test results are positive.
**For FOBT or FIT used as a screening test, the take-home multiple sample method should be used. A FOBT or FIT done during a digital rectal exam in the doctor's office is not adequate for screening.

Ask your doctor which tests are available where you live and which option is best for you. To learn more about these screening tests, see "Can Colorectal Polyps and Cancer Be Found Early?"

If you notice a change in bowel habits, dark stools, rectal bleeding, cramping/abdominal pain, or persistent weakness and fatigue, see your doctor right away. Most of these symptoms are likely to be caused by conditions other than colorectal cancer, but they could also be signs of colon cancer so you should get checked out immediately. Don't wait – you have a much better chance of fighting colon cancer if it's found early.

For more information, see Detailed Guide: Colorectal Cancer.