Isotonix Vitamin D with K2 contains vitamin D3, the metabolically active form of vitamin D, along with vitamin K2, a form of vitamin K which supports vascular health and calcium utilization. Vitamin D plays an important role in bone health, heart health and immune support while working with vitamin K to support normal absorption of calcium, and promote healthy arteries. Isotonix Vitamin D is the first of its kind to deliver both of these powerful vitamins with isotonic delivery. Vitamin K is included in Isotonix Vitamin D with K2 because of its unique partnership with vitamin D. Vitamins K and D work together to support calcium absorption and utilization. Vitamin K supports the normal delivery of calcium to the bones and promotes healthy arteries. At least two naturally occurring forms of vitamin K have been identified and are known as K1 and K2. While there are many similarities between these two forms of vitamin K, they are distinguished by their important differences. The most significant difference between K1 and K2 is their chemical structure, which results in different pharmacokinetic properties. Vitamin K1 is retained primarily in the liver where, at high doses, it may interfere with the action of warfarin and other anticoagulant medications. Vitamin K2 has a different mechanism of action. It is transported primarily to bones and blood vessels. Vitamin K2 helps to maintain bone mass, support calcium utilization and promote elasticity of blood vessels. Some studies have concluded that vitamin K2 does not interfere with anticoagulant medications.* However, most products containing vitamin K (including K1 and/or K2 ) warn users taking anticoagulants not to take the product. If you are currently taking warfarin or another anticoagulant medication, you should consult your physician before taking any product containing vitamin K1 or K2 .