Vitamin B₁₂ is an important cofactor for energy metabolism. It works with folate in the methylation 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 enables 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 is the predominant active isomer in the bloodstream. By promoting SAMe production, methylcobalamin maintains healthy cell development, including the formation of red blood cells.