The metallic element present in chalk and other forms of lime. The chief preparations used in medicine are calcium carbonate (chalk), calcium chloride, calcium gluconate, calcium hydroxide, calcium lactate, and calcium phosphate. Calcium gluconate is used intravenously to treat symptomatic calcium deficiency, for example in premature babies.

Calcium is a most important element in diet; the chief sources of it are milk and cheese. Calcium is especially needed by the growing child and the pregnant and nursing mother. The uptake of calcium by the baby is helped by vitamin D (see APPENDIX 5: VITAMINS). A deficiency of calcium may cause TETANY, and an excess may result in the development of CALCULI (stones) in the KIDNEYS or GALL-BLADDER.

The recommended daily intakes of calcium are: 500 mg for children, 700 mg for adolescents, 500–900 mg for adults and 1200 mg for pregnant or nursing mothers.