Vitamin B12 is an important cofactor for energy metabolism. It works with folate in the methionine synthase pathway, which supports healthy homocysteine metabolism in the synthesis of S-adenosyl-methionine (SAMe), an important methyl donor. As such, it supports methylation for key biochemical reactions occurring in blood cells, neurons, the vasculature and many other tissues. Through this pathway, Vitamin B12 is required for proper red blood cell formation, neurological function, and DNA synthesis. The activated and methylated form methylcobalamin is the primary form found in the cytosol of cells and predominates in blood and other fluids. This is the form of vitamin B12 primarily used for SAMe production, making it an important nutrient for healthy cell development, including red blood cells.