can b12 injections cause weight gain & Loss: What the Evidence Says – Bolt Pharmacy Will a Vitamin B12 Deficiency
Description
The Pernicious Anaemia Society notes this is well recognised but not fully understood

Vitamin B12 shots are generally safe for most people, but certain medical conditions may increase the risk of side effects or require careful consideration before starting the treatment

AOD-9604
Sun Y, Sun M, Liu B, et al

W., Yang T

It is possible that compensatory mechanisms could develop that reduce efficacy with prolonged use
