The Best Calcium Supplements to Buy and What to Avoid

Calcium supplementation and what to look for when buying

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Calcium supplements are available throughout the United States and Canada in different forms. There are four types of calcium supplements available for purchase. The most frequently used and effective calcium supplements are calcium carbonate and calcium citrate. The other two, calcium gluconate and calcium lactate, contain less elemental calcium are not as readily available as the other types. Here we outline what you can expect from each type of calcium supplement so you can make an informed choice.

Elemental Calcium

Not all calcium salts contain the same amount of elemental calcium. Elemental calcium is the amount of calcium actually absorbed by the body, for example there is more elemental calcium in calcium carbonate than in calcium gluconate. Make sure the label of the calcium product you choose lists the amount of elemental calcium, as well as the total calcium. If the phrase "elemental calcium" is not listed, find another calcium supplement.

Calcium Carbonate

Calcium carbonate, also known as calcite, is a mineral or salt used to help prevent the bone loss that occurs in osteoporosis. Calcium carbonate is the active ingredient in most OTC antacids such as Tums. Calcium carbonate is inexpensive and comes in tablets (including chewable tablets), capsules, and liquid. Calcium carbonate contains 40% of elemental calcium making it the highest concentration of calcium in supplement form for maximum absorption.

This type of calcium supplement is usually taken three to four times daily. Breakfast is the best time to take calcium carbonate because the body absorbs it best when taken with a low iron meal. 

Calcium Citrate

Calcium citrate absorbs about as well as calcium carbonate; however, it may be a better calcium supplement choice for people with reduced levels of stomach acids.

Fortified fruit juices often contain calcium citrate malate. While calcium carbonate absorbs best when taken with food, calcium citrate works equally as well when taken with or without food. Other types of calcium include calcium gluceptate, oral calcium gluconate, calcium lactate, and calcium phosphate.

The Importance of Magnesium and Vitamin D for Absorption

When using calcium supplements, it's important to remember that magnesium and vitamin D are essential in assisting with the absorption of calcium so that you will achieve the maximum benefit of your supplementation. Many calcium supplements also include vitamin D. You may also find calcium supplements that include both magnesium and vitamin D together. Another point to make about absorption is that calcium can prevent absorption from other vitamins and minerals in meals, therefore it is generally taken between meals, at least 2 hours after eating to avoid those negative side effects. 

How Much is Enough Calcium?

Taking more than 500 mg of calcium at one time is not recommended.

This is because your body cannot absorb more than 500 mg of calcium at one time. If you take more than 500 mg of calcium per day, make sure you spread your doses out over the course of the day. Talk with your doctor if you have questions regarding the daily amount of calcium that you should be taking.


CDC Online. Nutrition For Everyone. Basics.

Calcium and Vitamin D For Bone Health. UpToDate. Dietary Supplement Fact Sheet. Office of Dietary Supplements - National Institutes of Health. 

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