Scared of CT Scan help?

I am going to have a CT Scan next week. I am scared of the side effects from the iodine injection and that it will damage my kidney later on. Should I bring enough water and drink it after the scan so I can flush out the iodine in my system? help? I heard the side effect of iodine can be fatal? I am having a CT scan on my neck and possibly head? What do you think the exposure of radiation will be on those two areas?