Hi Nigela
I had a colonoscopy 2mths ago & was really scared my anxiety about taking meds would get in the way but I was fine. The centre i went to gives sedation unless you request otherwise, they also give buscopan if the bowel goes into spasm. The sedation & muscle relaxant are given intravenously so just one sharp prick & its over. I felt a little pain initially but then woke up in recovery 2hrs later, I dont remember anything about it. I went home after seeing the dr & getting my results & was fine. I did feel tired & didnt go to work the next day just slept it off. I was starving hungry though!
To be honest all my fears were unfounded. The preparation is unpleasant but if you make sure you drink plenty of water & follow the instructions to the letter you will be ok. I also suffer from migraine & was worried about dehydration but didnt get one.
I hope it goes well for you, it really is nothing to worry about.