If you have a first degree relative (parent, child, sibling) with colon cancer, you should begin having
screening colonoscopy when you are 10 years younger that the age at which that realtive was diagnosed. For example, my father died at age 50 and his colon cancer was diagnosed postmortem. That meant I should have begun having screening colonoscopy testing at age 40. I did not know this, and did not have a colonoscopy until I had symptoms at age 46.