It is sometimes called vitamin K3,[3] although derivatives of naphthoquinone are not naturally occurring chemicals and therefore do not qualify as vitamins, and without the side chain in the 2-position they cannot exert all the functions of the K vitamins. Menadione is metabolized by the human body into K2 which uses alkylation to yield menaquinones (MK-n, n=1-13; K2 vitamers), hence is better classified as a provitamin.
It is also known as "menaphthone