Men and women who are average risk for colon cancer (i.e. no family history of colon cancer or colon polyps, no history of inflammatory bowel disease or any other significant risk factors) should begin colon cancer screening at age 50 and age 45 for African American individuals.
Patients at a substantially increased risk have a family history (a first-degree relative with colon cancer or advanced adenoma/polyp diagnosed at any age) and are advised to have a screening colonoscopy starting at age 40, or 10 years younger than the earliest diagnosis in their family, whichever comes first. Repeat colonoscopies should be done every five years for those with more than 1st degree relatives with colon cancer at any age or a single 1st degree relative diagnosed <60 years of age.
There are other tests available for colon cancer screening but a colonoscopy is the best because it allows both detection as well as removal of any polyps encountered.