Calcium carbonate is only one of the many compounds used in making calcium supplements. Calcium carbonate is an alkaline-based salt. That is why it is known to control acidity in the stomach. It also requires an acidic environment to get absorbed, and therefore recommended by doctors to be taken after meals. For more details, visit aragonite-crystal.blogspot.com/2021/09/how-helpful-is-calcium-carbonate-for.html