I'm linking to a recent video produced in the US about b12 deficiency. If you thought it was 'just a vitamin.' then I really think you need to watch it. In the UK our diagnostics and treatment are not actually as good as in the US. We also, since 2007 have supplemented foods with folate.
Please watch it. You need to (although some will think it is quite scary)
If you don't want to click on the link, either copy and paste or tap in Diagnosing and Treating B12 Deficiency in to Youtube, it should pick it up.
It was suggested by the Press Office at Mumsnet that I place this here (just to prove I'm not spamming you.)
Good Health to You and Yours!