5 Common Reasons People Give for Not Doing a Colonoscopy A colonoscopy is a screening test for colon cancer and is crucial for early detection. Despite the fear of discomfort or pain, embarrassment, fear of finding something wrong, time and preparation involved, or cost, these reasons should not deter one from undergoing the procedure. Colonoscopies are performed under sedation and are routine procedures performed by trained professionals. Early detection of colon cancer is key to a successful outcome, and insurance plans usually cover the procedure.