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Calcium is the most abundant cation in the body, appearing in combination with phosphorus in the ratio 2:1.5. It is essential for the formation of bones and teeth, blood clotting, normal muscle and nerve activity, endocytosis and exocytosis, cellular motility, chromosome movement prior to cell division, glycogen metabolism, and synthesis and release of neurotransmitters.

Sources include milk and milk products, egg yolk, shellfish, and green leafy vegetables. Most - 99% - is stored in the bones and teeth. The remainder is stored in muscle, other soft tissues, and blood plasma.

Regulation of plasma levels is by free exchange with body stores, and through the action of hormones such as calcitonin, parathyroid hormone and vitamin D. Excess calcium is mostly excreted in faeces, and in small amounts in urine.

Last reviewed 01/2018