The other day I injected C into my hip...I think I hit a vein, because it bled like the dickens.
About 2 minutes later, I got a weird feeling creeping up both arms from my hands. I started feeling weird, so I laid down. I got the same feeling across my back from arm to arm, and my heart started racing. I did some calming breaths, tried to relax, and everything calmed down within a few minutes.

I've been on C for over 3 years and never had a reaction before...any ideas?

yep! I would say that qualifies as one. I hope you feel better.

The insert says to call your neuro and not inject til you talk to him/her...but I have injected since then and no problem.

except...I have been getting whopping huge welts again which I hadn't gotten for over a year and a half...and a lot more bleeding.

Sounds like you may have injected into the blood stream. I've done this before too.
Personally I like to inject, and then rub the dickens out of the spot as if I were kneeding bread dough. You can't assimilate this stuff enough! When you thing you have completely dispersed the drugs though out the skin, kneed some more. Then I rub it down with liquid Benedryl.

Yes, that is the classic copaxone "fake heart attack" reaction. It's not dangerous at all, just scary. I know one woman who had two or three of those reactions over a 15 year period. I personally never had one in my year of taking it. I did however get the ocassional "bleeder". I got welts about half of the time.

Sounds like it was some type of reaction. I've had quite a few IPIR's that were really bad. Bad enough where the pressure in my chest was so bad I couldn't breath well. It's hard to describe but it was not fun. On the plus side, I knew what it was and just laid there until it subsided. It took about 10 to 15 minutes to fully go away.

And, if you hit a vein, that could be the reason for your reaction as well. Any time I hit a vein I had a reaction, not always the big bad ones, but a reaction that was not typical for me. Since I don't have a lot of fat on my mid to lower thighs, I always seem to hit a vein or muscle in there and would always react. So, I stopped shooting my thighs. That took care of that.

I would let your neuro know about the reaction and if you have any more. Over time, I seemed to have more of the IPIRs and have been off C for over a year now due to such. I may be going back on it though as I do think it helped me.