My doctor has talked to his friend the neurologist about my high serum reading of 1207. I am 66, a vegan, take h2 blockers and two years ago had a large dose of nitrous oxide for a broken arm manipulation. A short while after that I developed symptoms but put it down to the painful radius break that developed complications. Later I suspected B12 d and started taking cyanocobalamin but it didn't alleviate the symptoms although my reading had gone up to 500! I read up on it and decided my cells weren't absorbing the B12. My doc disagreed because my figures had gone UP again and my folate was high. I also had macrocytosis. He still did nothing! So I started taking methylcobalamin which I've taken now for 7 days. The shaking has stopped. However, my depression was worse before taking them so I had given in and started anti depressants also! My doc rang me and said the only reason I could have a high reading and it not be utilised is if I have a missing enzyme...very rare...nothing can be done about that. The active test is not reliable he said and that is why it isn't done widely on the NHS. He just hopes the antidepressants and the B12 sublinguals will do the trick. So do I.