I'm due my injection on 27th May but noticed pain in joints comming back, brain fog and tiredness. GP is unsure what to do. He retested blood about a month ago said B12 was now over 1000. Is that good? He said it was fine. He is now retesting bloods again next week for everything. He said maybe vitamin D deficiency. I am confused as I feel the same as when I initially went to Gp and he said I have low B12 and possibly Pernicious anemia? Can any one help my confusion.