i am low normal as well with my b12. My doc just recently upped me to every 3 weeks instead of 4 because I was having symptoms after the 3 week mark until I got my next injection. I do mine in my arm as well. W eare hoping this makes the difference. She said upping my dose or taking it too frequent wouldnt work because you just pee the extra out.
Talk to your doc about taking more or more frequent. Oh and i have had to have my dose increased with every surgery. Less ileum equals less absorption.