Calcium supplements are used by people to increase their intake of calcium, a mineral the body needs to make bones and teeth.

When you are choosing a calcium supplement, it is important to know the amount of elemental calcium in the recommended dose. Elemental calcium is the amount of calcium that is actually used by the body. Consumers are advised to look at the amount of elemental calcium in each tablet in a supplement, as opposed to the strength of each tablet, which includes other substances.

Types of calcium supplements include:

• Calcium carbonate, which is 40% elemental calcium.
• Calcium citrate, which is 21% elemental calcium. While lower in elemental calcium than calcium carbonate, calcium citrate is easier to digest and does not cause constipation as much as do other types of calcium supplements.
• Calcium gluconate and calcium lactate, which contain a low amount of elemental calcium.

A person who takes calcium supplements should drink plenty of water and take other steps to avoid constipation.

Coral, bonemeal, oyster shell, and dolomite contain calcium naturally but may also contain heavy metals, particularly lead.