When it comes to choosing a Calcium supplement, quality is of the utmost importance. NOW Bone Calcium contains microcrystaline hydroxyapatite, the exact form of calcium found in our own bones. As a result, this unique compound remains one of the most advantageous sources of natural calcium available. Enriched with a proprietary blend of synergistic nutrients including magnesium, phosphorus, zinc and vitamin D, NOW’s Bone Calcium is an excellent way to get the calcium your bones so desperately need to maintain structural longevity.