When Should You Get a Vitamin B12 Injection? Soza Clinic Main benefits of B12 injections 1) Increased energy & reduced fatigue B12 helps convert food into usable energy Deficiency often causes tiredness, weakness, and low stamina 2) Healthy red blood cells Prevents Gym goers spending monthly on vitamin B and C injections Have a f*cking word with yourself. Both are water soluble, so don't stick around for long in your system (12 14hrs) hence B12 Shots: Vitamin B12 Injections Benefits, Uses, Risks Dr. Axe