Vitamin B12 Injections Benefits & Where to Book Hydrate IV Bar Vitamin B12 shots Prescription injections used to treat severe deficiency, pernicious anemia, or absorption issues (e.g., Crohn's, gastric bypass). They provide rapid, 100% absorption directly into the bloodstream, bypassing the digestive system. Injectable B12 Vitamin And Syringe On Blue Background Stock Photo Download Image Now iStock How to self inject intramuscular vitamin B12 Overview Guy's and St Thomas' NHS Foundation Trust