Vitamin B12 deficiency can cause symptoms like headaches, fatigue, depressive mood, gastrointestinal issues, and more. While vegetarians are at a higher risk of vitamin B12 deficiency, it can affect non vegetarians too. Check How Quickly Does a B12 Injection Work? Timeline and Expectations Bolt Pharmacy A vitamin B12 deficiency can cause a range of symptoms, including some that appear in the mouth B12 Injections for Energy: Benefits and How It Works AZ IV Medics What Does a B12 Shot Do for You? Vitamin B12 Deficiency