Vitamin D Supreme provides a clinically useful dose 550 mcg 458% of vitamin D3 along with vitamin K as both K1 and the MK-7 form of K2. This formula contains higher therapeutic doses than Vitamin D Synergy for situations where more aggressive repletion is required. Vitamins D and K are essential for optimal bone and arterial health and for maintaining the immune system in proper balance.* The amount of vitamin D and K in this formula may be beneficial for those who do not get adequate sun exposure and/or dietary sources of these vitamins. Vitamins D and K work as a team. Thus, increasing doses of vitamin D will increase the need for vitamin K.