It has been estimated that about 90% of vegetarians and vegans may suffer such a deficiency
Metabolic Health & Insulin Sensitivity Modulation of NNMT activity has been associated with improved glucose handling and insulin sensitivity, suggesting potential benefits in metabolic syndrome and related conditions
In general cyanocobalamin isn't retained as long as hydroxocobalamin so maintenance dosing tends to be more frequent - think in the states they tend to do loading doses as daily for one or two weeks followed by weekly for a few months and then monthly
It's better for energy and metabolism, but doesnt suppress appetite
People taking metformin, the common diabetes drug, are known to develop B12 deficiency as well, and people who avoid animal products can be deficient
Contact your clinician if the lump grows, becomes hard or warm, or causes increasing pain