Why Do I Feel Worse After My B12 Injection: 6 Body Reactions BloomMD From $165 Groupon Feeling worse after B12 Injection: Answering concerns. La Vie Med Spa Medinaz Vitamin B12 Deficiency Vitamin B12 deficiency happens when the body does not have enough vitamin B12. Vitamin B12 is important for making healthy red blood cells and Struggling with B12 injection frequency? Here's what you need to know If you have Pernicious Anaemia (PA) or B12 deficiency due to autoimmune gastritis, NHS guidance is clear: You should