If you really want to make sure you’re out cold and have little chance of remembering anything of the procedure then you may ask your doctor for local anesthesia. Local anesthesia does carry more chance of side effects(one of which is getting sick to your stomach afterwards). Depending on your health conditions you may or may not be the best candidate for local anesthesia.

Sedation can be quite powerful. I opted to be sedated due to my fears of being sick to my stomach afterward and my doctor originally suggested it. However, if you are extremely anxious over this, it would be best to discuss it with your doctor and let them know your feelings. They will be best to advise you of the health risks involved with either of these options.

Make sure you are getting at least one or the other. If your doctor suggests you have a colonoscopy without either sedation or local anesthesia & cannot give you a reasonable medical reason why, then drop them & find a different doctor.