Which Calcium Supplements Are Third-Party Tested?

Our recommendation

Buy Nature Made Calcium 600 mg with D3

The lowest-cost calcium-only tablet on a testing list. USP checks the ingredients and their amounts, purity and how it is made. Each tablet adds 400 IU of vitamin D3. It is carbonate, so take it with a meal.

Buy on Amazon

• Take calcium without food, or have low stomach acid? You want citrate instead. None of the 5 calcium citrates we checked is on a testing list. The one we recommend is 21st Century Calcium Citrate + D3 Petites ($0.14 per 500 mg).
• Drug-tested in sport? Momentous Calcium is NSF Certified for Sport, which also screens for banned drugs ($0.57 per 500 mg).
• Prefer a chewable? Caltrate Gummy Bites are on NSF/ANSI 173 (no store we use lists a price, so we have not priced them).

✓ On a testing list (5)

An outside program checked each of these and lists it by name. USP Verified and NSF/ANSI 173 check that the bottle holds what the label says. NSF Certified for Sport also screens for drugs banned in sport. More on each list

1. 

   Nature Made Calcium Magnesium Zinc with D3

   ✓ USP Verified

   333 mg a tablet · carbonate · 200 IU vitamin D3 a serving · Take with meals. Also 133 mg magnesium and 5 mg zinc a tablet.

   $0.070 per 500 mg

   Buy on Amazon
2. 

   Our pick · cheapest calcium-only tablet on a list

   Nature Made Calcium 600 mg with D3

   ✓ USP Verified

   600 mg a tablet · carbonate · 400 IU vitamin D3 a serving · Take with a meal.

   $0.082 per 500 mg

   Buy on Amazon
3. 

   Thorne Calcium

   ✓ NSF/ANSI 173

   250 mg a capsule · dicalcium malate · no vitamin D · No food rule on the label.

   $0.47 per 500 mg

   Buy on Amazon
4. 

   Also screened for drugs banned in sport

   Momentous Calcium

   ✓ NSF Certified for Sport✓ NSF/ANSI 173

   250 mg a capsule · dicalcium malate · no vitamin D · Brand says 1 capsule in the evening.

   $0.57 per 500 mg

   Buy on Amazon
5. 

   Caltrate Gummy Bites

   ✓ NSF/ANSI 173

   250 mg a gummy · tricalcium phosphate gummy · 800 IU vitamin D3 a serving · With or without food.

   Not priced

   Buy on Amazon

Not on any testing list (3)

We searched all five lists and did not find these. They may be fine, but there is no outside listing you can check.

1. 

   Caltrate 600+D3

   Not on a public list

   600 mg a tablet · carbonate · 800 IU vitamin D3 a serving · Take with food.

   $0.070 per 500 mg

   Check price
2. 

   Nature’s Bounty Calcium 1200 mg with D3

   Not on a public list

   600 mg a softgel · carbonate · 1000 IU vitamin D3 a serving · Preferably with a meal. The label says to take 2 softgels (1,200 mg) a day and does not say to split them.

   $0.095 per 500 mg

   Check price

3. 21st Century Calcium Citrate + D3 Petites

   Not on a public list

   200 mg a tablet · citrate · 500 IU vitamin D3 a serving · Label: with a meal (its Amazon listing says with or without).

   $0.14 per 500 mg

   Check price

Prices are per 500 mg of calcium at each brand’s list price (Vitacost or Target where the brand’s store blocked our reads or shows no price), checked October 12, 2026, the same way our best calcium guide prices them. Caltrate Gummy Bites: no store we use lists a price.

What “third-party tested” means

A company outside the brand checks the product and lists it by name, so you can look it up yourself. There are two kinds. A contents program checks that the bottle holds what the label says, without harmful contaminants. A banned-substance program screens for drugs banned in sport, which matters only if you are drug-tested. “Third-party tested” printed on a label, with no program named, is the brand’s word.

How to check your bottle

1. Find the mark. Look for an NSF or USP mark. “Third-party tested” with no mark is a claim.
2. Open the program’s own list. USP Verified, NSF/ANSI 173, NSF Certified for Sport, Informed Choice, Informed Sport. Or search all five on our testing-list index.
3. Search the product, not just the brand. Caltrate’s gummies are on a list; its tablets are not.
4. Try the maker’s name. NSF files products under the company that makes them, such as Haleon for Caltrate.

Citrate or carbonate: which do you need?

If you take calcium with meals, carbonate is fine and costs less. The NIH says carbonate “is absorbed best when taken with food.”

If you take it without food, or have low stomach acid, pick citrate. The NIH says citrate “is absorbed well on an empty stomach or a full stomach”, and people with low stomach acid, most common in older adults, absorb it more easily. None of the 5 calcium citrates we checked is on one of these lists. The one we recommend, 21st Century Calcium Citrate + D3 Petites, costs $0.14 per 500 mg at list price.

Either way, take 500 mg or less at a time. The NIH says calcium is absorbed best that way. Most adults need 1,000 to 1,200 mg a day from food and supplements together, so many people need less from a pill than they think.

Not medical advice. Calcium can block some medicines, such as thyroid pills taken within 4 hours. Ask your pharmacist. More: citrate vs carbonate · how much calcium to take.

Questions

The best calcium supplement, ranked by cost per 500 mg · calcium guide.

Where each listing comes from

The entry as each program’s own list shows it, and the label we read for the dose.

NSF lists the daily amount as the serving: 4 Caltrate gummies (two servings of 2) and 2 Thorne capsules (1 capsule twice a day). We also searched NSF under Bayer (Citracal’s maker), Haleon (Caltrate’s), Nature’s Bounty and Nestlé, and found none of the unlisted products.

Sources

1. NSF/ANSI 173 (info.nsf.org), searched by company October 9, 2026. NSF Certified for Sport (nsfsport.com), listing 1692143 read October 9, 2026. USP Verified and Informed Sport from our copies of September 22, 2026; Informed Choice from our copy of September 22, 2026 (USP’s site blocks automated reads).
2. Labels: NIH Dietary Supplement Label Database (labels linked above), read October 9, 2026; Momentous from its product page. Prices: each brand’s list price (Vitacost or Target where named), checked October 12, 2026. We quote no Amazon prices.
3. NIH Office of Dietary Supplements. Calcium: fact sheet for consumers. Read October 9, 2026.
4. Recker RR. Calcium absorption and achlorhydria. N Engl J Med. 1985;313(2):70-73. PubMed 4000241