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 Optimal Vitamin B12 Dosage and Treating Deficiency Efficacy of different routes of vitamin B12 supplementation for the treatment of patients with vitamin B12 deficiency: A systematic review and network meta analysis Irish Journal of Medical Science (1971 ) How Quickly Do Vitamin B12 Injections Work? Prime Aesthetics B12 Injections vs Pills Baltimore: Which Works? A vitamin B12 injection is a shot that delivers B12 directly into your muscle, helping your body absorb it quickly (especially if your body struggles to absorb it from food or tablets)