What is vitamin K? Vitamin K is a collective term for a group of vitamins that contain a functional group of 2-methyl-1,4-napthoquinone.  Some examples of this compound include phylloquinone (vitamin K1) and menaquinone (vitamin K2). This vitamin is an essential vitamin, which means that it is not made in the body and it must be … Continue reading Vitamin K – everything you need to know