How Quickly Can I Expect to Feel Better After a B12 Injection? 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, Why Do I Feel Worse After My B12 Injection? Causes & Management Bolt Pharmacy If you've been feeling weak, foggy, or experiencing numbness in your hands and feet, it could be a sign of vitamin B12 deficiency. B12 is essential for nerve function and red blood