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 .Methyl cobalamin is used to treat vitamin B12 deficiency. Vitamin B12 is important for the brain and nerves, and for the production of red blood cells. Methyl cobalamin is sometimes used in people with pernicious anemia, diabetes, and other conditions.