Vitamin B12 is a nutrient that helps keep your body’s blood and nerve cells healthy and helps make DNA, the genetic material in all of your cells. Vitamin B12 also helps prevent megaloblastic anemia, a blood condition that makes people tired and weak. B12 injections are prescribed by a doctor and given intramuscularly, or into muscle. These are very effective at raising blood levels of B12 and preventing/reversing a deficiency.
