I know there is a very long thread on B12. I am working through it and am TOTALLY confused. Forgive me, but I've only been on the board a few days. Because I cannot absorb ANY kind of B12 due to the surgery I had on my small intestine (I do not have intrinsic factor that makes this possible) I get the cyna B12. Until last year I got two injections a month, but last year a nasal spray that is covered by my insurance was available so I have been using more than the prescribed amount. The only thing I can say is I never had the cognitive problems others with CFS do. This could be a coincidence, because I was starting to get neuro problems before the shots: I failed the tuning fork test. I will be reading about B12 but doubt I can absorb the sublinguals of other types.