NICE guidelines : Follow-up appointments for people receiving intramuscular replacement
1.6.10 Do not repeat the initial diagnostic test in people who are having intramuscular vitamin B12 replacement.
1.6.12 If a person has , or is suspected of having, an irreversible cause of vitamin b12 deficiency:
continue with lifelong intramuscular injections, even if their symptoms have improved or are no longer present, and
advise them to come back if symptoms get worse, reappear, or they get new symptoms.
You are right - "the initial diagnostic test" in 1.6.10 is vague, although 1.3 Diagnosing vitamin B12 deficiency starts with Initial tests 1.3.1 "use either total B12 (serum cobalamin) or active B12 (serum holotranscobalamin) as the initial test" - but maybe the "or is suspected of having ...." in 1.6.12 could be used, as her total serum B12 was initially very low. Malabsorption could not be ruled out as a cause unless this is "based on results of further testing or investigations" -1.5.17
Box 1 and Box 2 : There is a more useful list of common symptoms and signs of vitamin B12 deficiency, some of which no doubt cannot even now be ruled out as present, and common risk factors, which includes "family history of vitamin B12 deficiency or an autoimmune condition".
I think any GP would struggle to justify the nurse's opinion on this guidance alone, vague as it is ! Just awful that you keep on having to go through this - and certainly "lifelong" should require less opinionation.
If that's not a word, I've just made it one. Stick that in the guidelines !
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Help please!! 
I wrote a letter, and this is what I got back. 
Help my elderly mum - please 
