Oral vs. Intramuscular Vitamin B12 in Vitamin B12 Deficiency The Blood Project 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. Vitamin B 12 intramuscular injections are also used therapeutically to help restore energy and combat various symptoms related to such deficiencies. Vitamin B 12 is essential to the development of healthy blood cells, nerve Vitamin b12 Injection CardioMender, MD How Long Does Vitamin B12 Take to Work? Timeline & Signs Performance Lab