Calcium Calcium Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The
Calcium/cholecalciferol Calcium/cholecalciferol Calcium/cholecalciferol is a combination of a calcium salt (usually calcium carbonate) and vitamin D (cholecalciferol), available under many brand names and in many forms such as chewable tablets, coated tablets, and effervescent tablets. It is used to prevent and treat lack of calcium and vitamin D in the elderly, as well as adjunctive therapy for osteoporosis. Possible side effects include gastrointestinal problems, for example nausea and constipation. If very high doses are taken, signs of hypercalcaemia (too high blood calcium levels) have been described, such as stomach pain, vomiting, thirst, and tiredness. Extreme or long-term or overdose can theoretically