Hi RunnerRachel!
Rather than type my tremendously-long post over again, I'm going to direct you to the thread started by Rinkty-Dink titled "Rheumatoid Arthritis and Type 1 diabetes". Look for my post entered today at 2:24 p.m. today, my time. If you have any questions, I'll try to answer them...just reply on that thread or this one.
Best of luck to you!