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Ranking the best calcium supplements of 2021

Written by John Davis

Last updated: November 27, 2020

Just drink milk for strong bones, right? Sometimes it’s not quite that simple.

Calcium is one of the most important minerals in your diet. It’s been clinically proven to improve bone strength, especially when taken in combination with vitamin D.

If you want a better shot at stronger bones, our research team has ranked the best options on the market, plus gone in-depth on the benefits and side effects of calcium supplementation.

Rankings

1.  Citracal Calcium +D3 Slow Release

citracal

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Citracal is a rare bird among supplements: it’s cost-effective, lab-verified, and simple.

Citracal’s slow release formula means you take the dosage once per day.  Other calcium supplements need to be divided up into smaller doses throughout the day; otherwise, the calcium passes through your body too quickly and not all of it is absorbed.

The slow release formulation obviates this problem.

The supplement uses a binder called hydroxypropyl methyl cellulose to achieve this slow release effect.  Though it’s a long and technical chemical name, it’s a nontoxic plant-derived compound that forms a gel when it comes into contact with water.

This slows the rate at which calcium is released from the tablet into your digestive tract.

Citracal uses a blend of calcium carbonate and calcium citrate to provide the mineral source of calcium, and also provides 1000 IU of vitamin D per capsule alongside 80 mg of magnesium, which makes up 20% of your recommended daily intake.

Laboratory testing reveals that the supplement actually contains 1350 mg of calcium per tablet (the label reports 1200 mg) and almost exactly 1000 IU of vitamin D.  It also contains no heavy metals or toxic contaminants, and the lack of “extra” ingredients is a boon for anyone looking for a straightforward, no-nonsense calcium supplement to take daily.

2.  Bluebonnet Calcium Citrate and Vitamin D3

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The calcium supplement formulation from Bluebonnet is perfect for the minimalist: it contains very few extraneous ingredients.

In fact, aside from its stated vitamin and mineral content (250 mg of calcium, 200 IU of vitamin D), Bluebonnet Calcium Citrate contains only five other ingredients, and all of them are binders or stabilizers to keep the tablets intact.

Its laboratory purity ratings are excellent.  Independent testing has verified that it contains within 2.5% of its label-claimed calcium and vitamin D content, so you know you’re getting exactly what’s been promised on the bottle.

Because of the simplicity of the tablet design, you should take Bluebonnet Calcium Citrate in smaller, separate doses to get optimal results.

If your goal was to supplement your diet with 1000 mg of calcium (100% of your recommended daily intake), you would need to take four tablets of Bluebonnet Calcium Citrate per day.

Taking these at different times throughout the day, as opposed to all at once, is a more effective way to deliver your body the calcium it needs (1).

3.  Kirkland Signature Calcium Citrate Magnesium and Zinc

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Kirkland’s calcium offering might be the most cost-effective calcium supplement on the market.  Its formulation employs calcium citrate to deliver the promised calcium, as well as magnesium oxide and zinc oxide for the other three minerals included in the tablets.

Each tablet provides 250 mg of calcium, 40 mg of magnesium, and 5 mg of zinc.

Not only that, it can hold its own in the analytical lab, too.  The analytically determined calcium content is exactly 250 mg per tablet, though its vitamin D content is actually about 30% higher than the claimed value.  This is not a concern, as vitamin D can be taken in much higher doses without any ill effects.

4.  GNC Calcium Plus 1000

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This is one of the brands you’re likely to be able to find in-person at a brick and mortar store.  GNC’s calcium supplement is straightforward and no-nonsense: each caplet contains 333 mg of calcium, 266 IU of vitamin D, and 166 mg of magnesium.

Like a few other supplements, GNC Calcium Plus exceeds its stated mineral contents by a good margin.  According to independent lab testing, each tablet contains a 28% excess of calcium and an 11% excess of vitamin D.

GNC Calcium Plus is a good choice if you’re primarily looking for a solid dosage of calcium and vitamin D at a low cost per-dose, without any extra frills like plant-derived calcium, a slow-release formula, or other minerals like zinc.

5.  New Chapter Bone Strength Calcium

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New Chapter Bone Strength is pretty standard, save for its calcium sourcing. The calcium in New Chapter Bone Strength is derived from algae—most supplements use a mineral source, either calcium citrate or calcium carbonate. It’s a nice feature if you want naturally-sourced calcium.

6.  Nature Made Calcium with Vitamin D

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Nature Made Calcium contains 600 mg of calcium and 400 IU of vitamin D, along with several binders and stabilizers in each softgel.

Notably, this supplement also includes some of the same binders used in Citracal’s extended release formulation—it’s likely that this product also has a slow-release effect, which is what allows it to have more calcium per tablet than other supplements.

Lab testing reveals that Nature Made Calcium with Vitamin D is fairly well-controlled in its manufacturing.  The capsules contain exactly the claimed amount of calcium, and an 18% excess of vitamin D.

7.  Swanson Calcium Citrate and Vitamin D

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The calcium and vitamin D offering from Swanson Health Products is another one for the simplistic camp.  Each tablet contains 310 mg of calcium and 200 IU of vitamin D.  The only other ingredients are vegetable-based binders and stabilizers.

If you are looking for zinc or magnesium alongside your calcium and vitamin D, you’re out of luck, but the good news is that Swanson’s calcium supplement sources all of its calcium from calcium citrate, which is a more readily-absorbed form of calcium than calcium carbonate, which is used in some other supplements.

It scores well on purity, too: lab testing found that the actual calcium content was only 13% higher than stated on the label, and the vitamin D content was 7.5% lower.

8.  Solgar Calcium Magnesium with Vitamin D3

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The calcium/magnesium supplement by Solgar is a minimalist-style supplement, even down to the packaging.

A simple amber bottle and brown label identifies the product, which consists of small tablets offering 200 mg of calcium each, alongside 100 mg of magnesium and 80 mg of vitamin D.

You’d need to take five tablets per day to reach 1000 mg of calcium—the Food and Drug Administration’s recommended daily intake.

In terms of its reported versus actual content, Solgar has some discrepancies.  Analytical testing found that the actual calcium content is 25% higher than reported, and its vitamin D content is 20% higher.

9.  Rainbow Light Food-Based Calcium

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Rainbow Light provides a moderate dosage of calcium in a food-based form, providing calcium alongside magnesium, betaine, spirulina, and a few other herbal ingredients. Unfortunately, it’s a bit heavy on additives, which lands it lower in the rankings.

10.  Solaray Calcium Magnesium Zinc

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You might term Solaray’s approach to calcium supplementation as the “maximalist” strategy.  Each capsule provides a pretty-standard 250 mg of calcium, 125 mg of magnesium, and 6 mg of zinc.

The magnesium is likewise sourced from a variety of ingredients; magnesium oxide, magnesium citrate, and magnesium amino acid chelate round out the magnesium sources.  The zinc is only from one source, an amino acid chelate. It’s a good pick if you care a lot about a variety of mineral sources, but most users will be better-suited by other supplements.

Category winners

Best calcium overall: Citracal Calcium +D3 Slow Release

Citracal wins big-time on two fronts: first, its calcium and vitamin D dose are fantastic. Second, its slow-release formulation means you don’t have to worry about the limits on bioavailability that come along with a standard calcium supplement. Thanks to these advantages, it’s the best overall choice. 

Best calcium for bone health: Bluebonnet Calcium Citrate and Vitamin D3

If you want to follow the scientifically-validated template for taking calcium for bone health, Bluebonnet is the way to go. It is a straightforward, no-nonsense calcium supplement with solid amounts of both calcium and vitamin D, to boost absorption. The only downside? You do need to take it several times a day for optimal absorption. 

Best calcium for women over 50: Citracal Calcium +D3 Slow Release

Women over 50 need high doses of both calcium and vitamin D, and the slow-release formulation of Citracal is a great way to ensure your intake is high without the trouble of taking four or five different capsules every day. 

Best calcium for better sleep: Nature Made Calcium with Vitamin D

When taking calcium for sleep, rapid absorption is key for maximum benefits. The softgel formulation of Nature Made Calcium means the calcium gets absorbed much more quickly than a tablet or traditional capsule. 

Best calcium supplement for osteoporosis: Bluebonnet Calcium Citrate and Vitamin D3

For the same reasons Bluebonnet wins out for bone health overall, it also takes the crown for osteoporosis: this supplement follows the template established by high-quality scientific research when it comes to slowing and reversing the loss of bone density associated with osteoporosis. 

Best calcium supplement for men: Kirkland Signature Calcium Citrate Magnesium and Zinc

Inadequate calcium intake can be a problem for men, too. Men benefit from Kirkland’s calcium supplement thanks to its inclusion of magnesium and zinc—deficiencies in these minerals are quite common in older men, and are associated with lower testosterone levels (which also contribute to poor bone strength).

Who should buy calcium?

Calcium supplements are primarily useful for people looking to retain or improve their bone mass, as well as prevent fractures related to low bone density.

People who will benefit from a calcium supplement can be placed into one of three categories. The first is older adults (particularly women) who already know they have low bone density. For them, supplemental calcium is a scientifically validated way to slow the rate of bone loss and decrease the risk of fracture.

The next category of people who can benefit from a calcium supplement are middle-aged adults who want to ensure they maintain their already-strong bone density. For these users, combining calcium supplementation with regular exercise is a good way to maintain strong bones throughout adulthood.

Finally, female teenagers can take advantage of the effects of calcium to actually build up substantial amounts of bone density.

Partially due to the hormonal changes that happen during puberty, girls who do not have sufficient calcium intake will not increase their bone density as much during puberty, and the gap between calcium-deficient and calcium-sufficient girls in terms of bone density lasts for the rest of their lives.

How we ranked

Since calcium is one of the most popular supplements on the market, we started with a field of dozens of potential products for our rankings.

First, we looked for supplements that provided enough calcium for optimal dosing throughout the day. We eliminated anything with less than 200 mg of calcium, and gave strong preference to supplements with 250 mg or more per tablet.

Calcium uptake is linked strongly to the presence of other micronutrients, most notably vitamin D, magnesium, and vitamin K.

Because of this link, we also required that all of the products that made the final rankings have at least some of these vital nutrients that are required for your body to make the most of the calcium you take. To make the top five, a product had to offer at least 200 IU of vitamin D.

We based this on research that demonstrates that calcium supplementation is more effective when accompanied by at least 800 IUs per day of vitamin D supplementation.

Next, we examined which supplements actually contained the label-claimed amounts of calcium and, when available, vitamin D.

We used results from independent laboratory testing to compare how supplements stacked up, and cut the supplements whose actual micronutrient content was vastly different than what was claimed on the label.

Lastly, we looked at the other ingredients in the supplement. Were the capsules vegan-friendly? Did they contain a lot of fillers and binders?

As always, we had a strong preference for a clean, simple ingredient design, and ranked these supplements highly. Our top performer, Citracal, stood out for its innovative slow release design that mitigates the need to take calcium several times per day.

Benefits

Calcium supplements are a good way to ensure your bones are as strong as possible when you get older.  Calcium salts are one of the primary constituents of skeletal bones, and without sufficient calcium intake, you risk having low bone density and osteoporosis.

This is not just a concern for older people; much of your ultimate lifetime bone density is determined in adolescence, and insufficient calcium intake in middle age can cause bone density loss to accelerate sooner and more rapidly (7).

Osteoporosis is a major public health concern.  According to a 2014 study by Nicole C. Wright and other researchers at the University of Alabama Birmingham, 10.3% of all adults age 50 or older in the United States have osteoporosis.  Osteoporosis is often seen as a women’s health issue, and indeed, about 80% of these cases are in women (representing almost 16% of all women over age 50).

However, there were still over two million men over 50 in the United States who have osteoporosis (8).  On top of this, an even larger fraction (some 44% of all adults over 50) of the population has low bone density—these people are at risk for developing osteoporosis in the future.

The good news is that there are some well-known ways to help prevent osteoporosis, and calcium supplementation is one of them.  Calcium supplementation seems particularly effective when combined with vitamin D, which boosts calcium absorption (9), and exercise plays an important role in preventing bone loss.

In fact, one 1991 study found that calcium supplementation alone was significantly less effective at preventing bone loss than calcium supplementation combined with exercise (10).

Calcium supplementation can prevent osteoporosis-related fractures in both men and women. Increased bone density from a calcium supplement is great, but does it translate into a reduction in osteoporosis-related fractures?

Fortunately, this too is a highly-researched question, and the answer appears to be a yes. A study published in the New England Journal of Medicine described an experiment that demonstrated these effects (11).

The study involved almost 400 men and women age 65 or older who took either a placebo supplement or a calcium and vitamin D supplement over the course of three years. The researchers found that, as we would expect, bone density increased. Moreover, the risk of having a bone fracture decreased significantly.

The results of this study mean that calcium supplementation reduces the risk of serious injuries linked to low bone density, meaning that the increase in bone density from calcium supplements is sufficiently large enough to prevent bone fractures.

Calcium supplements can help female athletes prevent stress fractures. Osteoporosis-related bone fractures aren’t the only consequences of inadequate calcium intake.

Athletes in training might be at a greater risk for stress fractures in their legs if they aren’t getting enough calcium. A study on female Navy recruits, who experience a high rate of stress fractures because of the demands of basic training, put this idea to the test (12).

In the study, published in the Journal of Bone and Mineral Research, over 5,000 female Navy recruits were recruited and randomly assigned to either a control group, which received a placebo supplement, or a calcium and vitamin D group, which took 2000 mg of calcium and 800 IU of vitamin D per day.

After eight weeks of training, the researchers found a 20% reduction in the incidence of stress fractures in the calcium supplementation group compared to the control group.

This suggests that female athletes doing sports that have a high risk of stress fractures, like soccer, running, and basketball, should consider taking a calcium supplement to reduce stress fracture risk.

Be sure not to take your calcium supplement at the same time as an iron supplement, though, since calcium can inhibit iron absorption.

Recommended dosage 

When it comes to what kind of calcium supplement to take and what dosage you should aim for, there are some pretty solid guidelines that can be found in the scientific research.

A 2007 scientific article in the medical journal The Lancet pooled 29 randomized clinical trials of calcium supplementation for reducing loss of bone density and conducted a meta-analysis on the results (13).

Drawing from a population of over 63,000 study participants, the researchers found that calcium supplementation results in a substantial and statistically significant reduction in the risk of bone fracture and in the rate of bone density loss.

Note that supplementation does not increase bone mass—that’s very difficult to do once you’re into your thirties, forties, or fifties.

Pooling massive sets of data like this allows you to find some pretty cool trends.  For example, the researchers found that the compliance rate of any given subject—i.e. how often they took the supplement—was associated with a 24% lower risk of fracture, meaning that sticking to your supplementation schedule pays big dividends.

On top of that, there’s clear evidence for optimal dosing.  Clinical trials that used dosages of more than 1200 mg of calcium and more than 800 IU of vitamin D per day were more successful than those that used less.

The recommended daily intake for calcium is only 1000 mg and the recommended daily intake for vitamin D is only 400 mg—the evidence from the research indicates that these values might need to be revised upwards, at least for adults over age 50.

As for the constituents of the supplement itself, there are a number of studies that suggest that, all else equal, a calcium supplement that contains calcium citrate is superior to one that contains calcium carbonate.

The citrate form of calcium appears to be absorbed more effectively, as demonstrated by a 1988 study by Jean A. Harvey, Margaret M. Zobitz, and Charles Y.C. Pak (14).

Side effects

While conventional wisdom holds that an excess of calcium in your diet, either through supplementation or normal dietary intake, puts you at risk for kidney stones, scientific research shows that the opposite is true—if anything, a high calcium intake reduces your risk of kidney stones.

This was the finding in a 1993 study published by Gary C. Curhan and other doctors at Harvard School of Public Health; a prospective study of 45,000 men aged 40 to 75 found that calcium intake was inversely related with the risk of kidney stones, i.e. more calcium equals fewer kidney stones (15).

There is some conflicting evidence on whether high levels of calcium supplementation may be associated with an increased risk of heart disease.

On one hand, a 2007 study conducted in New Zealand found that calcium supplementation increased risk of heart disease and stroke among postmenopausal women (16).  On the other, a 1998 study by researchers in South Carolina, Minnesota, and Pennsylvania found that high levels of calcium intake reduced the rate of heart disease in postmenopausal women (17).

The jury is still out on this, so you should talk to your doctor if you’re concerned about the effects of supplementation on your dietary risk.  There’s no one answer for everyone; whether supplementation makes sense for you depends on your diet, your overall health status, and your risk for heart disease, osteoporosis, or both.

Finally, calcium does interact with some other nutrients in the body, most notably iron. Supplemental calcium can out-compete iron for absorption, so if you are also trying to increase iron levels in your body, don’t take your calcium supplement at the same time as an iron supplement or a high-iron meal.

The effect is high enough that iron absorbed from a cheeseburger is significantly less than a hamburger without cheese, so you definitely don’t want to discount the interactions between calcium and iron.

FAQ

Q: What foods are rich in calcium?

A: Dairy is the most obvious type of food that’s rich in calcium; milk, yogurt, and cheese are all excellent sources of calcium.

Beyond dairy, though, other foods like almonds, kale, broccoli, beans, and even salmon are rich sources of calcium.

Some fortified foods, like breakfast cereals, also contain calcium, but it’s added in a low-cost supplemental form, not a naturally-occurring form.

Even with a lot of foods in your diet that are high in calcium, it’s still important to make sure your vitamin D intake is also high, because without vitamin D, you can’t make use of the calcium in your diet.

Q: Who is at risk for calcium deficiency?

A: Women are at a particularly high risk for calcium deficiency during and after menopause, because their hormone levels change in a way that is not favorable for calcium metabolism. These hormonal changes can also start to induce bone loss, so the need for calcium in these women is particularly acute.

Girls in adolescence are also affected by calcium deficiency, which is particularly serious considering the importance of high calcium intake on building bone density during adolescence.

Finally, vegans, vegetarians, and people with milk allergies or lactose intolerance are at a high risk for calcium deficiency because one of the major categories of calcium sources (dairy) is off-limits to them.

Q: How do you take calcium supplements for best absorption?

A: Calcium supplementation can be tricky to get right, because your body’s ability to actually absorb calcium is limited by a number of factors.

First among these is saturation of your body’s calcium absorption capacity. Generally, you don’t want to take one large, single dose of calcium per day, because much of it will pass through your system without getting absorbed.

To solve this, take your calcium three or four separate times during the day. Additionally, make sure your calcium supplement has vitamin D in it as well—this vitamin is essential for proper utilization of calcium in your body.

Finally, to avoid disrupting your iron metabolism, try not to take your calcium supplement at the same time as meals that are high in iron.

This can get tricky, though, because calcium supplements that use calcium carbonate ought to be taken with food. One way to get around some of these restrictions is to take a slow-release calcium supplement, like our top pick of Citracal—you only need to take one capsule per day of a slow release formulation like this.

Q: Are calcium supplements bad?

A: For most people, calcium supplements are good, not bad. Calcium supplements have a well-demonstrated record of increasing bone density and decreasing fracture risk in older adults.

Still, there are some people who should exercise caution with calcium supplements. While the evidence is inconclusive, some research has suggested that people who have very high calcium intake might have an increased risk of heart disease.

At the same time, while high dietary intake of calcium is associated with a decreased risk of kidney stones, some research suggests that high supplemental intake could increase the risk of kidney stones.

These findings, while tenuous, suggest that you might want to talk to your doctor if you know you are at a high risk for heart disease, or a high risk for kidney stones, before taking a calcium supplement. For these people, the potential risks need to be weighed against the potential benefits for bone health.

Q: What are the best calcium supplements for osteoporosis?

A: For osteoporosis, you want to look for three primary characteristics in a calcium supplement. First, you want the source of calcium to be calcium citrate, not calcium carbonate.

For healthy young and middle aged adults, calcium carbonate is fine, but because stomach acidity decreases as you get older, a calcium citrate based supplement can be easier to digest and absorb.

The other two characteristics to look out for are the calcium content and the vitamin D content: you want a supplement that makes it easy to get at least 1200 mg of calcium per day, and 800 IUs of vitamin D per day. These dosage recommendations come from large, well-designed scientific studies on treating and preventing osteoporosis.

You’ll notice that all of our top ranked calcium supplements, including Citracal, Bluebonnet, and Kirkland Signature, check all of these boxes.

Q: Is calcium citrate better than calcium carbonate?

A: Calcium carbonate is a common form of calcium used in supplements. It has the benefits of being inexpensive, though it relies on stomach acid to make the calcium biologically available. Moreover, the carbonate in this molecule will neutralize a small amount of stomach acid.

This is not a problem for healthy young people, but for older adults, whose stomach acid is already weaker due to aging, calcium carbonate might contribute to indigestion.

Calcium citrate can be a better source of calcium because it does not require stomach acid to become bioavailable and does not neutralize the acidity of your stomach. While both the citrate and carbonate forms of calcium are useful, citrate has a slight edge, particularly for older adults.

Q: How can you get calcium without dairy?

A: Vegans, vegetarians, and people with either a milk allergy or lactose intolerance face a much higher risk of calcium deficiency, because dairy is the biggest source of calcium in most people’s’ diets.

There are other foods, like almonds, kale, beans, and broccoli, that are high in calcium as well, but even so, it’s still not a bad idea to take at least a vitamin D supplement, if not a full on calcium and vitamin D supplement for maximum calcium absorption.

Q: How much calcium is in almond milk?

A: While almonds themselves have quite a lot of calcium, this calcium doesn’t make it into almond milk. As a result unfortified almond milk has very little calcium.

Fortunately, the best almond milk brands fortify their almond milk with both calcium and vitamin D. Our top pick in our almond milk rankings, for example, has a solid 450 mg of calcium per serving, plus 200 IUs of vitamin D.

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Recap

In sum, there is strong evidence that taking a calcium and vitamin D supplement can help keep your bones strong and reduce your risk of osteoporosis and bone fractures as you get older.  This is important as you approach your fifties, whether you are a man or a woman.

Look for a high-quality calcium supplement, ideally that uses calcium citrate as its mineral source, and definitely check to make sure your supplement includes a substantial amount of vitamin D as well.

If your goal is to prevent bone loss, you’ll get the best results with doses of at least 1200 mg of calcium and at least 800 IU of vitamin D per day.

To ensure you’re keeping your bones as strong as possible, add weight-bearing exercise like walking, jogging, or weight lifting to your daily routine, as calcium supplementation is most effective when combined with an exercise regimen.

For BodyNutrition‘s #1 calcium supplement recommendation, click here.

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John Davis

John Davis is a Minneapolis-based health and fitness writer with over 7 years of experience researching the science of high performance athletics, long-term health, nutrition, and wellness. As a trained scientist, he digs deep into the medical, nutritional, and epidemiological literature to uncover the keys to healthy living through better nutrition.