Hi India,
yes, I've had it. What do you want yo know? You'r only 18?? So young, I'm so sorry..
It's not painful, but you will be in isolation for a few days, maybe a week so take a book and lots of good food. Hydrating food, because you in a hospital with no fresh air and not a lot to do, you may as well eat.
In order for the iodine to "take", a patient must not have thyroxine in the system. In my day some years ago, I would have to come off my thyroxine for about 5 weeks prior to radioactive iodine. That was the worst bit. Really bad. Now though I think there are drugs that can block the thyroxine so you don't have to come off it.
After a thyroidectomy, radioactive iodine is a breeze, and kind of a holiday in the hospital. The whole experience though, I understand very well, is very traumatic.
Anything else, just ask!
Sarah.