Hi and welcome to Healing Well.
What other medications did your doctor start you on? How bad are your symptoms?
Many doctors prescribe mesalamine (oral, or oral and rectal) first to see if patients will respond to that, rather than jumping straight on pred, because of it's potentially nasty side effects. My doctor had me do that, and I was nearly in remission (and my flare was pretty severe), but then a tummy bug threw me back into the flare, so we started pred. You might want to consider asking your doctor what he thinks about
you giving the other meds a chance to work before starting pred.
When I was on pred, I had VERY little side effects. I had a small case of the munchies and I got slight moonface, but that's it. Not everyone is as lucky as I am, though. Many (if not most) of the members here have been on it at some point or another, and there is a very wide range in the severity of side effects. Weight gain/the munchies, moodiness, and insomnia, seem to be the most common.