A few points should be carefully weighed and analyzed before opting for a calcium supplement.

Purity: Choose calcium supplements with familiar brand names. Look for labels that state, "purified". Avoid calcium from unrefined oyster shell, bone meal, or dolomite because it may contain high levels of lead or other toxic metals.

Absorbability: Most brand-name calcium products are absorbed easily in the body. If you are not sure about your product, you can find out how well it dissolves by placing it in a small amount of warm water for 30 minutes and stirring it occasionally. If it hasn't dissolved within this time, it probably will not dissolve in your stomach. Chewable and liquid calcium supplements dissolve well because they are broken down before they enter the stomach.

Tolerance: Some people develop side effects with some calcium supplements, such as excessive gas or constipation. If simple measures (such as increasing your intake of fluids and high-fiber foods) do not solve the problem, you should try another form of calcium. Also, it is important to increase the dose of your supplement gradually: take just 500 mg a day for a week, and then slowly add more calcium. Do not take more than the recommended amount of calcium without your doctor's approval.

Calcium Interactions: It is important to talk to a doctor or pharmacist about the possible interactions between your over-the-counter and prescription medications, and calcium supplements. For example, calcium supplements may reduce the absorption of the antibiotic tetracycline. Calcium also interferes with iron absorption. So you should not take a calcium supplement at the same time as an iron supplement - unless the calcium supplement is calcium citrate, or unless the iron supplement is taken with vitamin C. Any medication that you need to take on an empty stomach should not be taken with calcium supplements.