3 Things to know before taking a calcium supplement

Calcium is the most commonly used OTC supplement, but is it really necessary to take one? Let’s understand more about calcium supplementation and what you need to know before taking one. 

On average, an adult would need around 1000 – 1200 mg of calcium per day. But due to several reasons like dietary inadequacy, medical conditions, personal choices or cultural practices, one might not be able to get 100% of the above recommended levels. That is when supplements come into play.


When your aim is to meet your recommended levels always choose natural sources of dietary calcium > fortified sources of dietary calcium > supplemental calcium.

There are different forms of calcium supplements available in the market, they are all basically a mineral (Calcium) + salt combination, as the elemental calcium needs to be bound with a substance to be taken orally. This then dissociates into elemental calcium when it comes in contact with various secretions in your gut and then finally reaches the blood via the brush border cells of your small intestine.

Different types of calcium supplements

The types of supplements differ mainly on the salt combination, there are almost 4 different types as listed below, but Calcium carbonate and calcium citrate are the most commonly used due to the higher percentages of elemental calcium present.

  • Calcium carbonate (40% elemental calcium)

  • Calcium citrate (21% elemental calcium)

  • Calcium gluconate (9% elemental calcium)

  • Calcium lactate (13% elemental calcium)

Other calcium forms in supplements include calcium sulfate, ascorbate, microcrystalline hydroxyapatite, and phosphate

Choosing the right supplement

Calcium carbonate has the highest percentage of elemental calcium making it the ideal choice but it does have its downsides. Since the absorption of calcium carbonate is dependent on the availability of stomach acid to disintegrate from its bound form to elemental calcium, it works well in individuals who have normal stomach acid secretion. It is also recommended to be taken with food as food inherently increases the secretion of hydrochloric acid in the stomach due to the activation of gastrin hormone during meal ingestion. People with medical conditions hindering gastric acid secretion like achlorhydria, gastric surgeries or similar conditions may not be a good fit for carbonate supplements. Also, those on medications like proton pump inhibitors, H2 blockers or antacids may also not benefit much from carbonate supplements.

Calcium citrate on the other hand does not need gastric juices for its digestion and hence can be taken on an empty stomach. However, due to the lower percentage of elemental calcium, a person may need to take extra doses to meet the required amounts of the supplements.

A word of caution - people with cardiac issues, kidney stones or kidney injury, gastric diseases and organ-related conditions need to check with their care provider before taking a calcium supplement.

One can choose from a variety of preparations including capsules, tablets, chewable pills, powder, etc. They all are fairly absorbed well, one can choose the form of supplement based on their routine or personal preference. For example, if a person does not have time to mix and prepare powdered solution then tablets and capsules can be a good option. If a person has swallowing issues then chewable forms or powdered forms might help.

Getting your dosage right

In most cases you may not need a 1200 mg supplement everyday (talk with your healthcare provider about the doses you might need to take for your conditions / complains) You can try to get 50-60% of your calcium from dietary sources that are high in calcium like milk products , tofu, fish, etc and the rest can be from the supplement. You can even choose calcium fortified foods to meet your needs.

It is always better to take supplements with food rather than on an empty stomach. 


The next important factor to keep in mind is “less is better” – 250-500 mg dose per meal is recommended rather than taking larger amounts all at once. This is because elemental calcium is best absorbed in smaller amounts. Taking doses more than that recommended by the manufacturer or your healthcare provider will not do any good and will only lead to complications.


Combinations of Calcium – Vitamin D – Magnesium or Calcium – Magnesium – Zinc are also available in the market, while they seem to be convenient in terms of a single pill taking care of multiple nutrients, it might have its own consequences. For example, if a person is not deficient in Vitamin D, magnesium or zinc, he/she might not need a combination supplement. Evenmore, taking it would lead to nutrient-nutrient interactions (Ex: Excess zinc can interfere with copper absorption) or lead to toxicity (Ex: when you have adequate vitamin D stores, this might lead to hypervitaminosis D)


Always try to fulfil nutrient needs from whole foods, if considering a supplement get to know what to consume, when to consume and how much to consume and never start on OTC supplements without discussing with your healthcare team.

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