liquid calcium is added with lysine, making the calcium more prone to be absorbed by the human body Calcium is a mineral that is found naturally in foods. Calcium is necessary for many normal functions of the body, especially bone formation and maintenance. Calcium can also bind to other minerals (such as phosphate) and aid in their removal from the body. Calcium carbonate is used to prevent and to treat calcium deficiencies. Calcium carbonate may also be used for other purposes not listed in this medication guide.