Ahcoleman, I understand that it was the methyl form but I don't think you are understanding me.
Not everyone can tolerate the methyl form. Ask for a different form next time, maybe the hydroxy form.
Also, you may have overmethylated and not needed a B12 shot at all.
Here are the links again:
Excessive vitamin B12 supplementation can cause anxiety, jitters, rapid heart rate, heart palpitation, and fatigue.
http://www.drlam.com/blog/mthfr-and-adrenal-fatigue-syndrome/4549/#sthash.WjSx3XDc.dpuf
What could you experience if you do take too much methylfolate?
– Irritability
– Anxiety
– Nausea
– Headaches
– Insomnia
This applies to both B12 and folate.
http://mthfr.net/methylfolate-taking-too-much-a-problem/2012/01/08/