Vitamin B12 Injections: What You Need To Know Oral vs. Intramuscular Vitamin B12 in Vitamin B12 Deficiency The Blood Project Cyanocobalamin is the preferred supplemental form of vitamin B 12 as there is insufficient evidence to support the efficacy of the other forms like methylcobalamin. Michael Greger MD, How Not to Die. 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.