What is the difference between Calcium Citrate and Calcium Carbonate?

Chemically, calcium carbonate and calcium citrate are not the same. Calcium citrate has a better absorption rate compared to calcium carbonate. However, the carbonate form has a higher calcium content compared to the citrate form.

Citrate contains 21 percent calcium, whereas carbonate has 40 percent calcium. Carbonate usually comes packed in large pills. Citrate is generally provided in an easier to swallow, convenient capsule form, which is why the price of citrate is higher. That and the body absorbs the citrate better; however, calcium in the citrate form can cause headaches and constipation. Calcium in carbonate form can produce gas and indigestion. Ironically, the carbonate form is also used as an antacid. Either types of calcium can help to bridge any gap where calcium is missing in the diet.