Many people take calcium supplements to help stave off bone loss, but how much calcium you actually get from a supplement isn't as straightforward as it may seem. Johns Hopkins explains …
In nature, calcium exists only as a compound (such as calcium carbonate or calcium citrate). Each compound contains a different amount of "elemental" calcium, the important ingredient needed for bone health.
When you take a calcium supplement, it's the amount of elemental calcium that's key. If the amount of elemental calcium isn't clearly stated on the bottle, check the Nutrition Facts label, which will include how much elemental calcium -- often listed simply as "calcium" -- is in a "serving size."
For example, Tums Ultra 1000 contains 1,000 mg of calcium carbonate per tablet, but only 40% of calcium carbonate is elemental calcium -- meaning, one Tums Ultra 1000 tablet has 400 mg of the essential mineral.
Often, the recommended serving size on the supplement label does not meet your daily calcium requirement. Tums Ultra 1000 lists a serving size as two tablets, adding up to 800 mg of calcium -- not enough for adults over 50, who should get 1,200–1,500 mg a day.
Bottom Line Advice: If you have questions about the right dosage, ask your doctor how many pills you should take each day. Also, it's best to spread out your daily dosage of calcium so you don' t take more than 600 mg of elemental calcium at one time; the body absorbs larger amounts less efficiently. Finally, take calcium carbonate with meals, because this type of calcium is absorbed better in the presence of stomach acid.