test-Your Complete Guide to Calcium Supplements
Joint Health
Your Complete Guide to Calcium Supplements
Medically reviewed by Dr. Patricia Weiser, PharmD • April 15, 2024

Choosing the Right Calcium Supplement

Calcium is a key mineral for supporting bone heath and many people choose to supplement with it.1 Similar to the many different types of magnesium supplements, there are numerous types of calcium to choose from... so how do you know that you’re taking the right type?

Types of Calcium: Comparing the Best Calcium Supplement Forms

When it comes to choosing a calcium supplement, there are several factors to consider, such as the amount of calcium it contains and how well your body can absorb and tolerate it.

Here’s an overview of the most popular types of calcium supplements:

Calcium carbonate is naturally found in organic material such as oyster shells and green leafy veggies like kale and broccoli.2 While calcium carbonate has one of the highest concentrations of elemental calcium (40%), it is not high in bioavailability. (Bioavailability refers to how well your body can absorb an active ingredient.) Taking calcium carbonate with meals and vitamin D can help improve its absorption.1

Some people may experience mild bloating or stomach upset with calcium carbonate.

This is a popular and economical form of calcium. Calcium citrate contains less elemental calcium than calcium carbonate, so it may require taking more tablets per day.3 The upside is that calcium citrate is easier for your body to absorb, even on an empty stomach.

Calcium lactate provides less elemental calcium (13%) than other types of calcium supplements. As such, calcium lactate may be associated with less bloating and constipation than calcium carbonate.4 It doesn’t contain lactose.

Microcrystalline hydroxyapatite (MCHA) is a component of our bones and teeth that provides rigidity and strength.5 Calcium hydroxyapatite as a supplement is typically derived from bovine bone, which is almost identical in structure to human bone.6 This is a moderately bioavailable form of calcium, but studies indicate that it’s useful for promoting bone health.

Since this calcium is sourced directly from bone,7 you’ll be supplementing more than calcium alone! MCHA also provides phosphorous, magnesium, other minerals and collagen.

As the name suggests, this type of calcium comes from coral. Coral calcium contains calcium carbonate. However, there are additional risks to coral calcium: unless harvested sustainably, these supplements can further endanger coral reefs. If you opt for coral calcium, make sure it is harvested from above-the-sea sources where no living coral is harmed.

Another marine source of calcium. There are downsides to this option, though. Most of the calcium from oyster shell is calcium carbonate, which is not very well-absorbed.

There’s More to It Than the Calcium Type

Perhaps more important than the type of calcium you take is how much you take, when you take it and what you take it with.

Elemental Calcium

Elemental calcium is a factor to consider when choosing a calcium supplement. The amount of elemental calcium varies in different calcium supplements. For example, calcium carbonate provides 40% elemental calcium, so a 1,250-milligram serving of calcium carbonate provides 500 mg of elemental calcium.1

Luckily, it’s easy to find on the package label in the Supplement Facts, so you don’t have to do any calculations. See below for an example of how elemental calcium is listed on our Calcium Citrate label.

Calcium Supplement Facts

The 200 mg of calcium listed is the elemental calcium contained in each capsule. It’s always important to look at a product’s supplement facts, because the amount of elemental calcium does not always equal the total amount of calcium. Below is another example of a supplement facts label from a coral calcium supplement.

Elemental Calcium Supplement Facts

While the supplement contains 1,000 mg of coral calcium, the total elemental calcium in each capsule is 350 mg. So always look for the elemental calcium on the Supplement Facts label to help you decide on a supplement and how much to take.

When to Take Your Supplements

Calcium is best absorbed in smaller doses of 500 mg or less. Taking more than 500 mg will not be absorbed well by the body. So, if you need to supplement 1,000 mg of calcium a day, you’ll divide it into 500 mg twice a day for the best absorption.

Since calcium supplements can cause stomach discomfort for some people, many opt to take it at mealtimes to avoid difficulty.

Combine with Other Nutrients for Better Absorption

If you’re not getting enough other minerals and vitamins, you likely won’t absorb calcium as well. This is because your body can’t absorb calcium without vitamin D and other nutrients. So, it’s important to also make sure you’re getting enough vitamin D, magnesium and vitamin K along with calcium.

More Isn’t Always Better

Yes, calcium is an essential mineral for your health, but taking more and more calcium isn’t always a good idea. You can overdo your supplements! The Recommended Daily Intake of calcium is around 1,000 mg for most adults, and unless your doctor recommends more there isn’t a reason to supplement beyond that.

You be well, now.


This article has been medically reviewed and accepted.

About Dr. Patricia Weiser, PharmD

Patricia Weiser, PharmD, is a Pennsylvania-licensed pharmacist and independent medical writer with over 14 years of experience in community and hospital pharmacy. She is dedicated to creating evidence-based health content that empowers individuals to take an active role in their healthcare. Areas of expertise include dietary supplements, over-the-counter medications, prescription drugs, vaccines, weight loss, cancer, eye care, and more. She has a Doctor of Pharmacy degree from the University of Pittsburgh.

*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.


1. Calcium and calcium supplements. Mayo Clinic. Read source

2. Calcium carbonate. StatPearlsRead source

3. Choosing a calcium supplement. Harvard Health. Read source

4. Clinical practice: Calcium supplements and fracture prevention. New England Journal of Medicine. Read source

5. Nutritional strategies for skeletal and cardiovascular health. National Library of Medicine. Read source

6. Hydroxyapatite. Science Direct. Read source

7. British Journal of Nutrition. Read source