The short answer is that it depends on which form of B12 you have
Over the past years, numerous ligands (for example, NBQX, NS102, NS3763, LY382884, LY377770, GYKI53655, UBP296, UBP301) with varying potency and selectivity have been synthesized to modulate AMPARs and KARs, several of which exhibit neuroprotective properties and beneficial effects in preclinical models of stroke, myocardial infarction, and brain injury (Matute, 2010)
Injections skip all of that
If you hear of someone dropping dead, particularly about a week after surgery or in a young healthy person, this is the number one concern
Why people choose Vitamin B12 injections Vitamin B12 injections deliver B12 directly into the muscle, which means absorption does not depend on the digestive system