It is not the use case being marketed to members of the public looking for faster recovery from training, or to biohackers looking for a longevity edge
Nature Reviews Immunology , 9 (11), 799809
We will not sell a course of B12 injections on the energy or weight-loss claim, full stop
People with dietary restrictions, such as vegans and vegetarians, who may not get sufficient B12 from their diet, or those with absorption issues, like those with pernicious anemia or gastrointestinal disorders, also often qualify
Injection site reactions Lipohypertrophy, irritation, redness, and bruising can occur at injection sites
IV Therapy When a shot is enough and when an IV may be smarter