Vitamin B12 deficiency can occur because of a poor diet, or because some medications interfere with absorption of B Vitamins. Some issues related to lack of B Vitamins are insufficient sleep, sleep apnea, chronic fatigue, and depression to name a few. Vitamin B12 is important for growth, cell reproduction, blood formation, and protein and tissue synthesis. Vitamin B12 shots effects lost around a week. Shots can be administered at home or in the office. Cyanocobalamin is the synthetic man-made form of vitamin B12, and due to its lower quality and potential ineffectiveness, we only use Methylcobalamin. This is an important distinction that anyone using B12 should ask their provider about.