NOW Foods Calcium Hydroxyapatite provides calcium in the microcrystalline hydroxyapatite form — the exact mineral complex that makes up 70% of natural bone tissue. Unlike calcium carbonate or citrate, hydroxyapatite is a complete bone matrix that contains not only calcium but also phosphorus, magnesium, and a full range of bone-building proteins and growth factors in their natural proportions — delivering the bone-building minerals in the form your bone cells recognize and use most efficiently. Clinical research, particularly from New Zealand and the UK, has demonstrated that microcrystalline hydroxyapatite is superior to calcium carbonate for increasing bone density and reducing fracture risk. Each capsule provides a meaningful calcium dose from this premium bone-matrix source. Manufactured in NOW's GMP-certified facility with identity and potency verification.