With respect to loading any vitamin. The concern is whether or not a patients serum levels are reflective of Total Body Stores and in many instances serum levels underestimate body stores. But is this relevant in a patient who is asymptomatic, NOPE.
Thus the utility of many laboratory tests are no better than the person who is interpreting those values in the context of THAT patient who sits before them!
To that end there are very few instances in which loading a vitamin or mineral is deemed medically necessary. A couple examples include patients with SEVERE SYMPTOMATIC iron deficient anemia and another is a patient who is given Vitamin K bc as a means of correcting hepatic related clotting dysfunction. (Another such example is patients who refuse blood transfusions on religious bases such as Jehova Witnesses and "bleed out" during a surgical procedure)
Those are the only two instances in which a PARENTERAL loading dose of either a Vitamin or mineral may be justifiablly "medically appropriate" IME.
Of course part of the reason the such loading meds Aquamephyton and Imferon are used as somewhat of a last resort is the risk of serious adverse effects, anaphylaxis in particular and although rare when it's happens to you or your loved one, that's NOT rare but real!
So really theres no way I could justify giving a patient B-12 shots unless they were symptomatic, had clinical features of a deficiency or a suppressed serum level AND even then I would advise ORAL therapy.
Who are candidates for PARENTERAL B-12 therapy? THOSE WHO HAVE A DEFECTIVE GI ABSORPTIVE MECHANISM/S, the remainder should be treated with oral agents.
Otherwise I'm beginning to believe some of you fellas enjoy the "rush" of being a pin cushion
JIM