Taking Vitamin B12? Read this first. While B12 is often hailed as a safe energy and brain booster, many real users are reporting unexpected side effects including anxiety, insomnia, Vitamin B12 (cobalamin) and folate (vitamin B9) are vitamins that serve important functions in the human body. Folate is needed for development and growth of cells (including red blood cells) and synthesis How Vitamin B12 Injections Impact Weight Loss Side Effects AlabamaAgeline.gov 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 keeping nerves B12 Shots: Vitamin B12 Injections Benefits, Uses, Risks Dr. Axe