I'm on Betaseron 4 months now. I don't use the arms at all because I don't have enough fat there. I know the auto-injector has a 10 (mm?) and a 8 extender to screw on the end of it if the 12 is going in too deep and hitting muscle. You just need to call Beta-Plus and ask them to send one out to you. I manually inject because I feel more in control of things and the sound the auto-injector makes makes me flinch. I had some small dots of bruising the first 2 months or so, but not anymore. I inject the outer areas of my thighs, stomach and buttocks. My outer thighs have a bit more fat there than the tops.

As far as the post injection side effects, I take 600 mg Ibuprofen a half hour before I inject . Perhaps a bit of joint pain the day after. In the first 2 months or so, I had some slight headaches the day after, but now very little if any side effect . It's recommended to hydrate more the day after the injections.

Good luck, pf. I hope your injections start going better for you. Have you tried calling your Beta nurse?