Is Calcium Citrate Better Than Calcium Carbonate?

Written By: Gloria Tsang, RD

Title: Founding Registered Dietitian

Alumni: University of British Columbia

Last Updated on:

Which calcium supplement is the best? This has got to be one of the most asked questions on HealthCastle! That’s partly because the topic is popular – many women take calcium supplements. But it’s also because calcium supplements come in many varieties.

A Note About Elemental Calcium

Before we discuss which calcium supplement is better, we must first talk about the most important factor when purchasing calcium supplements. When purchasing calcium supplements, look for the elemental calcium content, not the total content. For instance, a supplement containing 500 mg of calcium carbonate provides 200 mg of elemental calcium. Hence, the calcium supplement in this example only provides 200 mg of calcium, not 500 mg. Most brands now list the elemental calcium content on the back panel.

All About Calcium Citrate

  • Brands: Citracal
  • Absorption: Calcium is best absorbed in an acidic environment, so calcium citrate is the best absorbed supplemental form of calcium. It does not require extra stomach acid for absorption, so you can take it at any time during the a day, even on an empty stomach.
  • Calcium content: Calcium citrate usually provides less elemental calcium per pill than calcium carbonate, so you may need to take more pills per day to meet your needs. To elaborate, a 500 mg calcium citrate supplement only provides 105 mg of elemental calcium.
  • Pill size: Calcium citrate is usually small and in capsule form.
  • If you suffer from acid stomach, it is best to avoid calcium citrate.

All About Calcium Carbonate

  • Brands: Tums, Caltrate, and most other brands
  • Absorption: Calcium carbonate is alkaline based. It requires extra stomach acid for better absorption, so it is best taken right after meals or with a glass of acidic juice such as orange juice.
  • Calcium content: Calcium carbonate is the most prevalent calcium supplement in the market. It provides more elemental calcium than calcium citrate, so you may not need to take as many pills. As in the example explained in the elemental calcium section, a 500 mg calcium carbonate provides 200 mg elemental calcium.
  • Pill size: Calcium carbonate usually comes in a bigger tablet; some people may find it harder to swallow.

Other Types of Calcium Supplements

  • Dolomite, bone meal, or oyster shell: These naturally occurring calcium supplements may contain heavy metal or lead. At the moment, calcium supplements are not tested by any regulatory agency for lead content. Therefore, it’s best to avoid these.
  • Calcium gluconate and calcium lactate: These types of calcium supplements contain a very low amount of elemental calcium. Therefore, you will need to take a large amount of tablets to meet the calcium requirement!
  • Coral calcium: This type of calcium is marketed for more than bone health. An infomercial claimed that it can cure 200 human diseases. It’s actually only calcium carbonate! Read Coral Calcium Scam Alert!

More is Not Better

Your body can only absorb 500 mg of calcium at a time. Therefore, it is not a good idea to take 1000 mg of supplements in one sitting.  It’s best to split your dose throughout the day.

How Much Calcium Should I Supplement?

It depends. Depending on age and gender, the daily calcium requirement ranges from 1000 mg to 1300 mg for adults, so you need to do some calculations based on your calcium-rich food intake (one serving provides ~250 mg to 300 mg). If you do not eat enough servings of these foods, you may need to supplement.


calcium, osteoporosis, pregnancy, supplements


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