Vitamin B12 Injection Dosage for Adults: 7 Key Medical Guidelines Liv Hospital Hydroxocobalamin Injection: Vitamin B12 for Energy & Anemia Mountainside Medical How Often Can I Take B12 Injections? Vitamin B12 injections deliver high doses of this essential vitamin directly into your bloodstream for better absorption than oral supplements to boost energy, support red blood cell production and maintain nerve function. How Long Does Vitamin B12 Take to Work? Timeline & Signs Performance Lab