I only give myself avonex in my thighs. I just rotate around to different spots. I noticed when I took it in my deltoid (upper arm) that I had the full blown flu-like symptoms - fever of 103, chills that had the bed shaking, and horrible body aches. It was definitely the worst reaction ever. When I talked to my avonex nurse about it, she said that she recommends only doing the arm shots after you've been on it for at least 6 months. Not sure why, but probably something to do with it being a smaller muscle and changing the absorption. Good luck with whatever you decide.