vitamin b12 injection is given where Best Site: Administering B12 Shots How to Give a B12

While all B vitamins play roles in energy metabolism and cell health, B12 is especially crucial for brain, nerve, and blood function

Sterile water has no preservative and should only be used if you plan to use the entire vial immediately

Further, NICE and the BNF says that if there are neurological symptoms present, then every other day injections are the recommended treatment, so all the points you make about B12 being stored and sufficient are not really relevant

In research settings, it is studied for its role in energy metabolism, nerve repair, and cognitive support

Thereby, ketamine as the model of schizophrenia in rats [193] (as acute ketamine administration was associated with schizophrenia-like or psychotomimetic symptoms with large effect sizes and an increase in positive and negative symptoms [195,196]) might escape from the extraordinary complexity of extrapolation from animal models of mental disorders in general [197,198,199]