Vitamin K is an essential, fat-solube vitamin that cannot be synthesized by the body, making supplementation necessary. Vitamin K is a group of three vitamins: Vitamin K1 (phylloquinone), Vitamin K2 (menaquinone), and Vitamin K3 (menaphthone), which is synthetic. Menaquinone-7 (MK-7) is the active isomer of Vitamin K2 and has the highest bioavailability and longest half-life in the blood.