Jarrow Formulas Bone UP - Superior Calcium Formula - Microcrystalline Hydroxyapatite with Potassium Citrate & MK-7 - Combines Microcrystalline Hydroxyapatite (MCHA) with vitamin K2 as MK-7 (a more bioavailable form of vitamin K) and vitamin D3 to support the deposition of calcium into the bones as well as to assist in building up the organic bone matrix. Potassium citrate is also added for optimal osteo support.