this list is not exhaustive Antacids Colchicine (treatment of gout) H2 Blockers (Zantac, Tagamet, Pepcid) Metformin Diabetes drug (Glucophage) PPIs Proton pump inhibitors (Omeprazole, Nexium, Prevacid, Protonix) Nitrous oxide anaesthesia Nitrous oxide recreational abuse (Laughing gas / Whippets / Hippy crack) Mycifradin sulphate (Neomycin) antibiotic Para aminosalicylates antibiotic Phenytoin (Dilantin) anti-epileptic Potassium chloride (K-Dur) Cholestyramine (Questran) Chemotherapy and radiation treatment Increased demands Chronic Hemoltic anaemia Hyperthroidism Multiple myeloma Myelopproliferative disorders Neoplasms Pregnancy Some patients may never find out the cause of their condition, this does not mean that they should be denied B12 injections which are, safe, inexpensive and the most efficient treatment for their deficiency

The standard NHS schedule For a confirmed deficiency, the NHS treatment pathway sets out: Loading phase: 1mg of hydroxocobalamin on alternate days for up to two weeks (longer if there are neurological symptoms), to refill your stores
I will have to learn that, it may be the better option
Though this is speculative rather than evidence-based
But if your deficiency is caused by an absorption problem, lifestyle tweaks will not replace the injection schedule, they only support it
Cellular efficiency