Vitamin K comes in two main forms with distinct roles in the body: vitamin K1 (phylloquinone) and vitamin K2 (menaquinones MK-2 through MK-14). While all forms support similar functions, K1 has a short half-life, stays in the blood for only a few hours, and is mainly used in the liver, whereas K2 circulates for days and is used more widely in tissues like the brain and bones. K1 makes up about 90% of dietary vitamin K but is poorly absorbed (5–10%), while K2 is almost fully absorbed and has high