A colonoscopy is a very safe procedure and is generally performed in an outpatient setting. The chances of something wrong occurring during a colonoscopy are very small with fewer than 1% of patients having complications. Potential risks include bleeding, perforation of the colon, sedation medication side effects, and, inability to visualize the entire colon or lesions. Your surgeon will discuss these risks with you and recommend ways to reduce the risks such as holding “blood thinning” medications.