Q. Since a woman is supposed to have 1,000 milligrams of calcium a day, why don't the calcium tablets contain 500 mg so she can take two a day if she gets little calcium in her diet? By taking two 600 mg calcium pills, she gets too much. Isn't it dangerous? Also, does a multivitamin have any calcium? If she takes one of these a day with calcium tablets, is there a risk of getting too much calcium?
A. A wide variety of calcium pills are available without prescription. While it is true that some contain 600 mg of calcium, tablets with 250 or 500 mg calcium can also be purchased.
The composition of multivitamin pills is similarly variable. Many contain no calcium. Others are supplemented with minerals such as calcium, iron and magnesium. The amount of calcium in these multivitamin preparations ranges from insignificant to as much as 500 mg.
Also, to calculate your total amount of calcium from the supplement, you must add the labeled amount of elemental calcium.
Tums, which are frequently recommended as an inexpensive form of calcium supplementation, contain 500 mg of calcium carbonate, but only 200 mg of elemental calcium.
The most recent revision of the Recommended Daily Allowances for men and women suggests 1,200 mg of elemental calcium daily up to the age of 24 and 800 mg a day after age 24.
Excessive calcium intake is only a danger for people with a disorder causing elevated blood levels of calcium or possibly in those with kidney stones containing calcium.