B12 deficiency:, Common symptoms signs, Unexplained fatigue, Peripheral neuropathy (numbness), paraesthesia (pins and needles), gait disturbance, falls, Cognitive change, memory problems, B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics Vitamin B12 and Nerves Vitamin B12 Deficiency Vitamin B12 deficiency happens when the body does not have enough vitamin B12. Vitamin B12 is important for making healthy red blood cells and keeping nerves