Are there any reliable tests available to prove (or otherwise) that someone is B12 deficient? In 2008 in Spain I was diagnosed, after six months of illness and unexplained symptoms, by a test for homocysteine levels. I was given weekly loading doses for 1 month thereafter 3 monthly and became fit again. Some years later after traumatic events and relocation to the UK my injections were missed and after some months of returning symptoms I finally, with PA society's help and advice, got the UK doctor to resume my injections but only 3 monthly with no initial loading doses. I have found that my symptoms are returning after only a month and have been supplementing with tablets and oral spray. The doctor refused to give me injections more frequently but recently said would review after a blood test. That came back at over 700 so have now been told I can have one more injection only (13 weeks since the last) thereafter tablets only as the level is so high. Where do I go from here? Is there no way of proving that B12 is needed? I am frankly scared as my neurological symptoms are becoming marked.