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Difference Between Calcium Citrate & Carbonate

author image Nadia Haris
Nadia Haris is a registered radiation therapist who has been writing about nutrition for more than six years. She is completing her Master of Science in nutrition with a focus on the dietary needs of oncology patients.
Difference Between Calcium Citrate & Carbonate
White calcium pills on a table Photo Credit Anthony Hall/iStock/Getty Images

Not all calcium supplements are the same; you may have noticed that some types contain calcium citrate, while others contain calcium carbonate. While both of these provide a healthy dose of this mineral, they may differ in how easily your body absorbs calcium. Consult your doctor before taking supplements of any kind. You may need a calcium supplement if you are not getting adequate amounts of calcium from your diet.

Calcium Citrate

Your body can best absorb calcium in an acidic environment, and because calcium citrate is an acidic molecule, it doesn't need stomach acids for easy absorption. Registered Dietician Gloria Tsang advises that if you have low levels of stomach acid, your body will more easily break down and use calcium from calcium citrate. However, this supplement form typically contains less elemental calcium per pill than calcium carbonate, and so you may need to take an increased dose. Additionally, if you suffer from excess stomach acid, calcium citrate can worsen your symptoms.

Calcium Carbonate

Likely, you likely have a bottle of calcium carbonate in your cupboard; this form of calcium if found in many common brands of anti-acid tablets. Unlike calcium citrate, calcium carbonate is alkaline and requires extra stomach acid to digest and absorb it. Tsang recommends that you take it immediately after a meal or with a glass of orange juice. Remember that calcium carbonate gives you more elemental calcium per pill than calcium citrate, and so you may not need to take more than one pill or tablet at a time.

Proper Dosage

Most people get adequate amounts of calcium from their daily balanced diet. If you need to take calcium supplements, it is best to start slowly so that your body can adjust. Your body can only absorb 500 milligrams at a time, and the University of Maryland Medical Center recommends that you start with one daily dose the first week and then add a second daily dosage. The daily recommended dosage of calcium for is 1,000 milligrams per day; after age 50, women need 1,200 milligrams.

Things to Consider

Carefully follow the recommended dosage, regardless of the type of calcium supplement you take. Harvard Health Publications warns that in some cases, too much calcium can lead to hypercalcemia, a condition that can cause confusion, nausea, vomiting and nerve problems. Additionally, large doses of calcium from food or supplements can adversely interact with prescription medications such as antibiotics and with some types of blood pressure medications. Inform your doctor of all the medications and supplements you take.

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