Vitamin D Synergy™ provides clinically useful amounts of vitamin D3 and vitamin K (both K1 and K2 [as MK-4]), along with geranylgeraniol (GG), a substance produced naturally in the body, to promote optimal bone and arterial health and to maintain the immune system in proper balance. This formula may be ideal for those looking to maintain optimal vitamin D status in the body. It can be replaced with Vitamin D Supreme when higher targeted levels of vitamins D and K are desired. Vitamins D and K work synergistically, thus, increasing vitamin D increases the need for vitamin K.