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Calcium Carbonate Is Not Always the Best Choice

All salt forms do not have the same solubility, which means some dissolve more easily than others. Dissolution is required for absorption.

The most popular salt form is calcium carbonate, which contains the highest amount (40%) of elemental calcium. It looks like calcium carbonate is a pretty good deal because you’re getting a lot of calcium per dose. However, calcium carbonate is the least available to be absorbed once it’s taken. It requires an acidic environment, or lots of stomach acid, for absorption, so it is best taken with a meal. After a meal, your stomach produces more stomach acid and lowers the pH.

A more soluble salt form is more available than calcium carbonate for absorption when the pH of the stomach is higher, like it would be on an empty stomach or if you’re taking an acid blocking medication, such as Prevacid, Prilosec, Nexium, Zantac or any of the others currently available. If you are taking one of these acid blocking drugs or if you have low stomach acid, choose a more soluble salt, such as calcium citrate, lactate, malate or gluconate, to ensure maximum absorption and effectiveness.