Bioclinic Naturals B12 Methylcobalamin 5000 mcg is the cofactor in enzymatic reactions with diverse physiological functions. Methylcobalamin, the principal circulating form of B12 and the one transported into peripheral tissues, has been shown to support normal homocysteine levels, helps organize the body’s response to cellular damage, maintains cardiovascular health, and supports healthy neuronal function. B12 levels may be low due to inadequate dietary intake or insufficient absorption, which becomes more common with age. The 5000 mcg serving helps to provide additional support.