Natural Factors Vitamin K and D combines 2 fat soluble vitamins into one convenient soft gel. The form of Vitamin K is K2 (menaquinone-7, or MK-7, from natto bean), an advanced, fat-soluble form of vitamin K that serves multiple functions in the body. Vitamin K dependent proteins in our bones have revealed this vitamin's most important function is aiding bone development by acting as a regulator and director of calcium in the tissues. Vitamin D has long been considered a classic nutrient for bone metabolism. It supports bone development and is needed for calcium absorption. Vitamin K and D uses vitamin D3 (cholecalciferol), a natural form of vitamin D that is safer and more biologically active than D2 (ergocalciferol), a synthetic form of vitamin D. Evidence shows that vitamins K2 and D3 work synergistically to improve bone density. Those taking anticoagulant medication should consult their physicians before taking any supplements with Vitamin K.