How often do you obtain B12 injections for weight loss? Cyanocobalamin (B12) Injection 1000 mcg mL, Multiple Dose Vial 1 mL, 25 Tray McGuff B12 Injection Frequency: How Often Should You Get a B12 Shot? Liv Hospital Dr. prescribed B12 injections. Pharmacy only gave me vials. Where do you get your needles and syringes? What size?? Where do I inject? : r B12_Deficiency Do You Need a Prescription for B12 Injections? OmegaQuant