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 Is this the right size needle for im injections? : r B12_Deficiency How to Give a B12 Injection: Step By Step Instructions B12 vitamin Store Needle and Syringe Information for injecting vitamin B12 and vitamin C. Find out what needle sizes are recommended. VanishPoint 29 Gauge x 5 16 inch Retractable Insulin Syringe with Needle 1 mL, Regular Wall, 100 Box B12 vitamin Store Intramuscular vs Subcutaneous Injections for vitamin B12 supplements.