By far the worst part is what they refer to as the “bowel prep” i.e. strong laxatives. A top tip is to coat the affected area with Vaseline before starting!

That and the sedation depends on whether you’re getting a “flexible sigmoidoscopy” or a full colonoscopy. The latter is the full 1.5-2 metre insertion to inspect all the way to where the small intestine starts, which typically involves sedation (though conscious). The former is usually preceded by a home enema rather than laxatives and done with pain relief only.