Vitamin B12 Deficiency: Signs & Symptoms Vitamin B12 is essential for nerve health, red blood cell formation, and brain function. When B12 levels are low, symptoms often develop slowly and silently, Feeling tired all the time, tingling in your hands or feet, poor concentration, or burning feet could be signs of Vitamin B12 deficiency. Early diagnosis and proper treatment can help protect your Vitamin B12 shots: Uses, benefits, and side effects How soon do you feel less tired after a B12 injection? Vital Force IV Therapy