How Quickly Do Vitamin B12 Injections Work? Prime Aesthetics VITAMIN B12 (Generic) Injectable Solution, 1000 mcg mL, 100 mL vial Easy Refills Chewy Rx B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics 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. Luminous B12 Injections What is a B12 injection A B12 injection is a form of supplementation where vitamin B12 is administered directly into the muscle or under the skin, bypassing