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 Too Much B12 Symptoms: Overdose Signs & Safe Dosage Bolt Pharmacy Why Do I Feel Worse After My B12 Injection? Causes & Management Bolt Pharmacy Experiencing any of these symptoms? B12 supplementation might be right for you. Some causes of low B12 are diet, alcohol use, certain diseases like Chrohn's and Celiac Disease, and Gastric Bypass surgery,