where do they give vitamin b12 injections to Safely Inject B12: A Comprehensive Guide B12 vitamin Store How to
Description
A number of functions, including nerve growth, brain function, and red blood cell production, are dependent on vitamin B12

doi: 10.1158/2326-6066.CIR-14-0075

It reduces fatigue and helps you stay sharp throughout the day
[7] [4] Anti-intrinsic factor antibodies help diagnose pernicious anaemia

Those observations are included here only to summarize research context
If left unattended, the deficiency can lead to anemia, as well as nerve and brain damage, which may eventually become irreversible