Calcium is the most abundant mineral in the body, making up nearly 2% of total body weight. Our bodies contain a staggering 1200 g of calcium. Only 1% of this calcium is in the body fluids (the extracellular fluid, the blood, and the cellular fluid). The calcium in the blood is important for a number of functions, including blood clotting, transmission of nerve impulses, muscle contraction, stability of cell membranes, and cell metabolism. The remaining 99% of the calcium in the body is contained in the bones in the compound hydroxyapatite

Calcium requirements:

Age	Calcium Requirement
9-18	1,300 mg/day
19-50	1,000 mg/day
51+	1,200 mg/day

The pregnant women and nursing women definitely require a little more amount of calcium during the course.

Common calcium containing foods include milk, cheese, yogurt, and calcium-fortified orange juice. Soy milk fortified with calcium, fish canned with its bones (e.g., sardines), dark green vegetables, nuts and seeds, and calcium-processed tofu are additional sources. In general it’s safe to take up to 2,500 mg of calcium daily. Greatly excessive intake of calcium can cause numerous side effects, including dangerous or painful deposits of calcium within the body.

Calcium absorption studies have found that your body can't absorb more than 500 mg of calcium at one time. Therefore, it is most efficient to take your total daily calcium in two or more doses.