B12 Shots: Vitamin B12 Injections Benefits, Uses, Risks Dr. Axe 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 Long Does a Vitamin B12 Injection Last? Skin Benefits & More Signs and Symptoms of Vitamin B12 Deficiency B12 Injections: What's the Buzz? Vitamin B12 is the star of several essential functions in the body. However, it's common to be deficient in B12 and as a consequence experience fatigue,