Can anyone explain to me why this is, my symptoms now when my b12 feels low, are far worse than they were just 2 years ago before my diagnosis. I was diagnosed with a b12 serum of 103 ( 240-700) my last b12 serum was <1500. I have had to go from every 12 weeks with extra supplements to every 6 weeks either extra supplements to every two weeks with no supplements and I'm now feeling like every week is needed. Presumably when I was first diagnosed my b12 must have been dropping slowly, I know for a fact that I was at least a year with it untreated. It was picked up in hospital after I had a stroke, my then Gp didn't treat it as in his words, "there is nothing to indicate a b12 deficiency" so its a puzzle as to why I feel worse now white a much higher b12 level that I did with a much lower actual deficient level?