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 Headache After B12 Shot: 3 Effective Strategies to Feel Better Vitamin B 12 Injections in Denver, CO Let's Face It Med Spa Feeling worse after B12 Injection: Answering concerns. La Vie Med Spa B12 Shot or B12 InfusionWhich is Right for You? Both options deliver B12 effectively. B12 Infusions (IV's) provide extra hydration and nutrients and takes up to 45 50 minutes to administer, while B12 How Quickly Do Vitamin B12 Injections Work? Prime Aesthetics