Side effect form B-12 OR?

I now after 1 yr. and 1 mo. post op. have to take a b-12 shot. I have to take the shot 1x a week for 1 mo. and 1x a month there after. A strange thing has been happening and just thought it may be a bad side effect from the shot. First off the first shot was give to me on Wed. the 21st. then Wed. the 28th. The shot on the 21 first made me tired and then by Friday I was on turbo speed LOL. But I was noticing in my left arm on my vein it was really putruding out ward like I was getting ready to have blood drawn. I have a bad pain in it all the way to my wrist. Then the pain went always by sun. Then on Wed. when I got the new shot I am going threw the same thing swollen puffed up vein with pain with pain. I do not take this shot in a vein it goes in the muscle. The first shot was in my Rt arm. the second shot was in my Rt. hip. So why the pain in the left arm in my vein? I am thinking I should be seen for this. Anyone have this problem. I have so much energy it's scaring me

That is really strange! My Mom and daughter take B12 regularly for pernicious anemia. (I'm sure it is just a matter of time for me!) The energy burst is pretty typical. You are suddenly able to make red blood cells. I have seen my 89 year old mom perk up in a matter of hours after the shot. The part that is strange is the vein pain. I have never heard or seen anything like that associated with B12 shots. I hope this symptom goes away for you! Joy