Screening for colon cancer with a colonoscopy is actually done every 10 years. It begins at age 45 for those who are at average risk. And if a person has an immediate family member, this includes mom, dad, brother, sister, who has colon cancer, then the screening is done 10 years before their cancer was diagnosed, or at the age of 40, whichever one is earlier. It’s very important, therefore, to know your family history. Once polyps are detected, then colonoscopies are generally done at sooner intervals. And this usually is about every three to five years, but this should be determined specifically by your doctor.