Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Testing evidence
Evidence status
Recognised certification
Manufacturer statement
NSF registry page lists 'Thorne® Calcium' under NSF/ANSI Standard 173 Dietary Supplements, with finished product entries for 'Thorne® Calcium' at two facilities. Thorne’s own page also states: 'This product has been third-party tested and certified to verify what's in the package matches what's on the label and to confirm it contains no unsafe levels of contaminants...'
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Testing evidence
Evidence status
Recognised certification
Manufacturer statement
NSF registry page lists 'Thorne® Calcium' under NSF/ANSI Standard 173 Dietary Supplements, with finished product entries for 'Thorne® Calcium' at two facilities. Thorne’s own page also states: 'This product has been third-party tested and certified to verify what's in the package matches what's on the label and to confirm it contains no unsafe levels of contaminants...'
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Testing evidence
Evidence status
Testing claimed
Manufacturer statement
Manufacturer site says: "All our products undergo rigorous testing to ensure you are receiving the purity, potency and guaranteed quality labeled on each product."
Compare elemental calcium in mg per labelled daily serving, not compound or tablet weight. Vitamin D, magnesium and other actives are recorded separately. The amount is what the label states, not a dose-adequacy rating. Where directions give a range, the range is shown and daily cost uses the low end (no directions: one unit a day). Read the dose guide ↓
NSF registry page lists 'Thorne® Calcium' under NSF/ANSI Standard 173 Dietary Supplements, with finished product entries for 'Thorne® Calcium' at two facilities. Thorne’s own page also states: 'This product has been third-party tested and certified to verify what's in the package matches what's on the label and to confirm it contains no unsafe levels of contaminants...'
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Nutrasource registry page for Ultra BoneUp® states: "IGEN™ Certified" and "This product has PASSED because it does not contain detectable amounts of genetically engineered GMO proteins and genes included in the IGEN™ testing panel."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says: “For over 30 years, 21st Century Vitamins has provided trusted vitamins and supplements… From sourcing the finest ingredients to rigorous testing and production processes, we ensure that every product meets our stringent quality benchmarks.” It also lists “ISO/IEC 17025:2017 Certified Lab” and “USP standards for heavy metals,” but I did not find an independently verifiable product-specific COA or registry entry for this calcium product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Nature Made’s product page states “United States Pharmacopeia (USP) Verified” and “USP has tested and verified ingredients, potency and manufacturing process.” USP’s own Quality Supplements registry lists “Nature Made Calcium 600 mg with Vitamin D3 Tablets” as a USP Verified Product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
NOW product page says: "Made and quality tested in the USA with globally sourced ingredients." NOW’s quality page also says it performs extensive in-house testing and partners with third-party labs, but I did not find an independently verifiable product-specific COA or certification for this calcium/magnesium tablet product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
NOW’s product page says: “Made and quality tested in the USA with globally sourced ingredients.” NOW’s quality page also says it partners with trusted third-party labs for independent verification, but I did not find a product-specific third-party COA or a certifying-body registry entry for this calcium hydroxyapatite product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Carlyle’s own site says the product is “Laboratory Tested” and that “we conduct testing in our microbial lab, examining for purity, potency, and composition,” but I did not find an independently verifiable third-party certificate or lab report for this specific calcium softgel product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Bronson’s own certifications page says: “Every product manufactured by Bronson is put through a rigorous process to ensure purity, potency and integrity… Bronson products consistently comply with the most current regulations to deliver premium supplements verified for quality and safety” and “From raw materials to finished batches, Bronson supplements undergo numerous laboratory tests to ensure quality standards are met.”
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says: "We put our products to the test, ensuring maximum potency from each formula we produce" and "test each individual product to ensure it meets our strict Quality Assurance Standards."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says this product is made with 'rigorous testing and production processes' and 'meets our stringent quality benchmarks,' but I did not find an independently verifiable third-party certificate/COA for this specific calcium product. The site also has a separate 'Heavy Metal Testing Results: Prenatal' page that says 'Click the link to view the full third-party heavy metal testing results for that batch,' but that page is for prenatal products, not this calcium citrate product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
KAL’s product page says: “Trust Built On Testing” and lists “Passed Testing for Heavy Metals,” “Passed Testing for Microbials,” “Passed Testing for Contaminants,” and “Passed Testing for Physical Properties.” The brand blog also says KAL “test[s] every batch of raw materials” and that “every product we make is backed by rigorous standards like ISO and cGMP,” but I did not find independently verifiable third-party lab reports or a certifying-body registry entry for this specific product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer About Us page says: "All of our products are manufactured following cGMP rules and guidelines and reviewed by a third-party independent laboratory. Tested. Our supplements are checked for purity, potency, and overall excellence."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says: "All our products undergo rigorous testing to ensure you are receiving the purity, potency and guaranteed quality labeled on each product."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
"All products are subjected to a strict quality assurance system put in place by our on-site laboratory, to test each product at every stage: from raw material to finished product."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says the product is 'produced in our GMP facility that is certified by NSF' and that ingredients are 'triple-tested to meet strict guidelines on potency, purity, and contaminants'; the product page also says 'Lab Testing Certifications' and 'Passed Testing for Heavy Metals / Microbials / Contaminants / Physical Properties.'
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer FAQ says: "every lot of AlgaeCal is tested for heavy metals, bacteria, molds, and more to ensure safety." Also the product sheet says: "Each batch of AlgaeCal bulk powder is lab tested for heavy metals and microbes by independent labs in the USA and Canada."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Thorne’s quality page states that “Every supplement we manufacture undergoes four rounds of testing” and that finished products are tested for identity, potency, purity, and microbiological contamination. However, I did not find an independently verifiable third-party COA or a certifying-body registry entry for this specific product, Advanced Bone Support (SKU SG822 / formerly Oscap).
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Pure Encapsulations’ Quality Assurance page says: “All raw materials and finished products are independently tested for purity and potency by our third-party laboratories.”
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Nature’s Way’s quality page says: “A dedicated team of 75 quality experts tests every raw material we receive. Then they test the formulas throughout manufacturing, and finally, the product before it goes to you.” The product page also says “Tested & Trusted” and links to PureCheck, but I did not find an independently verifiable batch-specific COA or third-party certification for this specific product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
NSF registry page lists 'Thorne® Calcium' under NSF/ANSI Standard 173 Dietary Supplements, with finished product entries for 'Thorne® Calcium' at two facilities. Thorne’s own page also states: 'This product has been third-party tested and certified to verify what's in the package matches what's on the label and to confirm it contains no unsafe levels of contaminants...'
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Nutrasource registry page for Ultra BoneUp® states: "IGEN™ Certified" and "This product has PASSED because it does not contain detectable amounts of genetically engineered GMO proteins and genes included in the IGEN™ testing panel."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says: “For over 30 years, 21st Century Vitamins has provided trusted vitamins and supplements… From sourcing the finest ingredients to rigorous testing and production processes, we ensure that every product meets our stringent quality benchmarks.” It also lists “ISO/IEC 17025:2017 Certified Lab” and “USP standards for heavy metals,” but I did not find an independently verifiable product-specific COA or registry entry for this calcium product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Nature Made’s product page states “United States Pharmacopeia (USP) Verified” and “USP has tested and verified ingredients, potency and manufacturing process.” USP’s own Quality Supplements registry lists “Nature Made Calcium 600 mg with Vitamin D3 Tablets” as a USP Verified Product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
NOW product page says: "Made and quality tested in the USA with globally sourced ingredients." NOW’s quality page also says it performs extensive in-house testing and partners with third-party labs, but I did not find an independently verifiable product-specific COA or certification for this calcium/magnesium tablet product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Calcium form
Other calcium saltCapsuleMicrocrystalline hydroxyapatite (MCHA, 2,273 mg)
NOW’s product page says: “Made and quality tested in the USA with globally sourced ingredients.” NOW’s quality page also says it partners with trusted third-party labs for independent verification, but I did not find a product-specific third-party COA or a certifying-body registry entry for this calcium hydroxyapatite product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Carlyle’s own site says the product is “Laboratory Tested” and that “we conduct testing in our microbial lab, examining for purity, potency, and composition,” but I did not find an independently verifiable third-party certificate or lab report for this specific calcium softgel product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Bronson’s own certifications page says: “Every product manufactured by Bronson is put through a rigorous process to ensure purity, potency and integrity… Bronson products consistently comply with the most current regulations to deliver premium supplements verified for quality and safety” and “From raw materials to finished batches, Bronson supplements undergo numerous laboratory tests to ensure quality standards are met.”
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says: "We put our products to the test, ensuring maximum potency from each formula we produce" and "test each individual product to ensure it meets our strict Quality Assurance Standards."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says this product is made with 'rigorous testing and production processes' and 'meets our stringent quality benchmarks,' but I did not find an independently verifiable third-party certificate/COA for this specific calcium product. The site also has a separate 'Heavy Metal Testing Results: Prenatal' page that says 'Click the link to view the full third-party heavy metal testing results for that batch,' but that page is for prenatal products, not this calcium citrate product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
KAL’s product page says: “Trust Built On Testing” and lists “Passed Testing for Heavy Metals,” “Passed Testing for Microbials,” “Passed Testing for Contaminants,” and “Passed Testing for Physical Properties.” The brand blog also says KAL “test[s] every batch of raw materials” and that “every product we make is backed by rigorous standards like ISO and cGMP,” but I did not find independently verifiable third-party lab reports or a certifying-body registry entry for this specific product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer About Us page says: "All of our products are manufactured following cGMP rules and guidelines and reviewed by a third-party independent laboratory. Tested. Our supplements are checked for purity, potency, and overall excellence."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer site says: "All our products undergo rigorous testing to ensure you are receiving the purity, potency and guaranteed quality labeled on each product."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
"All products are subjected to a strict quality assurance system put in place by our on-site laboratory, to test each product at every stage: from raw material to finished product."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Calcium form
Mixed formsCapsuleCalcium citrate and calcium carbonate
Manufacturer site says the product is 'produced in our GMP facility that is certified by NSF' and that ingredients are 'triple-tested to meet strict guidelines on potency, purity, and contaminants'; the product page also says 'Lab Testing Certifications' and 'Passed Testing for Heavy Metals / Microbials / Contaminants / Physical Properties.'
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Manufacturer FAQ says: "every lot of AlgaeCal is tested for heavy metals, bacteria, molds, and more to ensure safety." Also the product sheet says: "Each batch of AlgaeCal bulk powder is lab tested for heavy metals and microbes by independent labs in the USA and Canada."
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Thorne’s quality page states that “Every supplement we manufacture undergoes four rounds of testing” and that finished products are tested for identity, potency, purity, and microbiological contamination. However, I did not find an independently verifiable third-party COA or a certifying-body registry entry for this specific product, Advanced Bone Support (SKU SG822 / formerly Oscap).
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Pure Encapsulations’ Quality Assurance page says: “All raw materials and finished products are independently tested for purity and potency by our third-party laboratories.”
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Nature’s Way’s quality page says: “A dedicated team of 75 quality experts tests every raw material we receive. Then they test the formulas throughout manufacturing, and finally, the product before it goes to you.” The product page also says “Tested & Trusted” and links to PureCheck, but I did not find an independently verifiable batch-specific COA or third-party certification for this specific product.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Calcium form
Mixed formsCalcium + DCapletCalcium carbonate and calcium citrate
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
Displayed points and weights are rounded; the total uses unrounded weights. Pending dimensions are excluded. Provisional scores may change after review.
One-time purchase prices; delivery and conditional discounts excluded. Daily cost uses the recorded label serving. Comparison amounts are not personal dose recommendations. Unknown Prime eligibility is not treated as confirmed.
Calcium forms and labels explained
Calcium carbonate and citrate differ in elemental-calcium density and stomach-acid dependence. Compare elemental calcium first, then consider the form, serving size and added nutrients.
Calcium carbonate
Common high-density calcium salt
Elemental fraction
About 40{3683f0b818e4e7eac3a25ad8212965194ab09621a23bd0189e97e17dfedff11f} by weight
Food context
Best taken with food
Higher elemental density is practical, but it does not make every carbonate product clinically superior.
Calcium citrate
Less stomach-acid dependent
Elemental fraction
About 21{3683f0b818e4e7eac3a25ad8212965194ab09621a23bd0189e97e17dfedff11f} by weight
Food context
With or without food
Citrate can be easier to absorb when stomach acid is low, but form alone does not prove better outcomes.
Other calcium forms
Less-common calcium sources
Examples
Lactate, gluconate, phosphate, hydroxyapatite
Compare
Elemental calcium
Do not assign a higher score merely because a form is less common or branded.
Calcium plus vitamin D
Combination formula
Calcium
Record elemental mg
Vitamin D
Record separately
Added vitamin D has its own dose, form and safety context.
Calcium dose: US RDA, Daily Value and upper limits
US calcium recommendations refer to total intake, not the amount everyone should get from supplements. The adult RDA is 1,000 mg/day at ages 19–50, 1,000 mg/day for men 51–70, 1,200 mg/day for women 51–70, and 1,200 mg/day from age 71. [1][11]
FDA's calcium Daily Value is 1,300 mg. [2] The DV is a label reference and should not replace the age/sex-specific RDA.
The total-intake UL is 2,500 mg/day for adults 19–50 and 2,000 mg/day from age 51. [1] A product label shows only supplemental calcium, so it cannot by itself prove whether a person's total intake exceeds the UL.
What the calcium evidence shows
Calcium is essential, but routine high-dose supplementation does not guarantee fewer fractures. A 2026 systematic review of 69 randomised trials involving 153,902 participants found little to no clinically important fracture or fall benefit from calcium, vitamin D or combined supplementation overall; most participants were community-dwelling and not at high fracture risk. [3]
Safety findings are not one-dimensional. The Women's Health Initiative found more urinary-tract stones with 1,000 mg/day calcium carbonate plus vitamin D than placebo. [4] Cardiovascular meta-analyses have reached conflicting conclusions, with a 2023 analysis finding no significant excess events and a 2021 analysis reporting increased CVD/CHD risk. [5][6]
Calcium evidence by goal
Evidence by goal
Goal
Evidence strength
What was assessed
Typical study context
Main limitation
Meeting adult calcium needs
Established nutritional requirement; supplement need varies
Total calcium from food plus supplements
Adult RDA varies from 1,000 to 1,200 mg/day by age and sex.
The RDA is not a supplement-only target.
Routine fracture prevention
Little to no clinically important benefit overall
Calcium, vitamin D and combined supplementation
2026 review of 69 RCTs and 153,902 participants; most were community-dwelling and not high risk.
Does not determine treatment for diagnosed osteoporosis, deficiency or high-risk institutionalized patients.
Choosing citrate versus carbonate
Clear practical absorption differences; no universal outcome winner
Calcium citrate and calcium carbonate
Citrate is less acid-dependent; carbonate is more elementally dense and meal-dependent.
Absorption and convenience do not prove better long-term clinical outcomes.
Kidney-stone risk
Signal in a major combined-supplement trial; broader evidence mixed
1,000 mg/day calcium carbonate plus vitamin D
WHI, 36,282 postmenopausal women, mean 7 years.
Combined intervention and specific population; other reviews have not uniformly shown increased risk.
Read the full evidence-by-goal detail
Meeting calcium needs
Supplements can contribute when dietary calcium is insufficient, but the amount needed depends on the person's food intake, age and sex. The RDA is a total-intake reference rather than a supplement serving. [1]
Fracture prevention
Current randomized evidence does not support assuming that routine calcium supplementation prevents fractures in generally community-dwelling adults. [3]
Choosing citrate or carbonate
Calcium citrate is less dependent on stomach acid and can be taken without food; calcium carbonate is more meal-dependent and provides more elemental calcium per gram of compound. [1] These are practical formulation differences, not a guarantee of better clinical outcomes.
When to take calcium
Calcium carbonate is best taken with food, while calcium citrate can be taken with or without food because it is less dependent on stomach acid. [1][10]
NIH reports that fractional absorption from supplements is highest at elemental-calcium doses of about 500 mg or less at one time. [1] A larger daily amount may therefore be split by a label or clinician, but this is absorption context rather than a universal personal dosing instruction.
Medicine timing matters too. Calcium can reduce absorption of levothyroxine, quinolone antibiotics and dolutegravir; follow the medication's instructions or a clinician/pharmacist's advice. [1]
Calcium safety, kidneys and medicine interactions
Who should be cautious?If any of the following apply to you, speak to a healthcare professional before taking Calcium - see the full detail below for why.
People with chronic kidney disease or known hypercalcemia
People with recurrent kidney stones
People with hyperparathyroidism or another disorder affecting calcium regulation
People taking levothyroxine, quinolone antibiotics, dolutegravir, lithium or other medicines affected by calcium
People using multiple calcium-containing supplements or calcium-containing antacids
The adult calcium UL applies to total intake: 2,500 mg/day at ages 19–50 and 2,000 mg/day from age 51. [1] A supplement-only table cannot determine total intake without knowing diet.
Higher supplemental calcium may increase kidney-stone risk in some settings. In the WHI, 1,000 mg/day calcium carbonate plus vitamin D increased reported urinary-tract stones. [4] NIH notes that other systematic reviews have not consistently found the same association. [1]
Cardiovascular evidence is also mixed rather than settled. [5][6] People with kidney disease, recurrent stones, hypercalcemia, parathyroid disorders or relevant medicines should use clinician/pharmacist advice rather than a generic product ranking.
Calcium with vitamin D and other minerals
Calcium is commonly sold with vitamin D and sometimes magnesium, zinc or other nutrients. Compare each ingredient on its own label basis. Added vitamin D does not change the elemental-calcium calculation, and a combined formula does not establish that everyone needs each included ingredient.
Use the separate Vitamin D comparison when the vitamin D amount or form materially affects the choice.
Who might consider a calcium supplement
A calcium supplement may be useful when food intake does not reliably meet the person's age- and sex-specific calcium requirement. NIH lists dairy foods, fortified beverages, some tofu and fish with edible bones among important sources. [1]
People using calcium because of osteoporosis, low blood calcium, kidney disease, recurrent stones or a medicine-related reason fall outside a simple retail comparison and should use clinical advice.
How to compare calcium testing evidence
Useful calcium testing evidence should confirm the finished product's identity and elemental calcium strength, identify relevant contaminants, and match the exact product or batch where claimed. Combination products should show whether added vitamin D or other minerals are also within scope.
FDA cGMP rules address identity, purity, strength, composition and contamination controls. [8] USP's voluntary verification program adds facility audit, documentation review, laboratory testing and off-the-shelf testing. [9] Neither cGMP compliance nor a quality seal proves that a calcium supplement prevents fractures or is right for a particular person.
Blood testing & your results
Serum calcium is tightly controlled by the body and is not a good direct measure of nutritional calcium status or dietary intake. [1] Blood calcium tests are clinically useful when a clinician is investigating abnormal calcium physiology, kidney or parathyroid disease and related conditions, but routine serum-calcium testing should not be recommended simply to choose a retail supplement.
Testing evidence in this comparison
A testing claim is not the same as a verified report. No public evidence located does not mean a product has not been tested.
Testing review pending0
Recognised certification2
Verified independent evidence0
Manufacturer COA0
Testing claimed17
No public evidence located6
What does calcium cost?
Current US comparison set, based on the daily serving shown on each label.
$0.03Lowest daily cost
$0.21Median daily cost
$2.83Highest daily cost
Your questions, answered
How much calcium do adults need in the US?
The RDA is 1,000 mg/day for adults 19–50 and men 51–70, and 1,200 mg/day for women 51–70 and adults 71+. [1][11] These are total-intake recommendations, not supplement-only doses.
Why does the label say 1,300 mg Daily Value?
FDA uses 1,300 mg as the calcium Daily Value for labels. [2] It is a labelling reference, while the RDA varies by age and sex.
Is calcium citrate better than calcium carbonate?
Citrate is less dependent on stomach acid and can be taken without food; carbonate is more elementally dense and is best taken with food. [1][10] That does not make either form a universal winner.
Should calcium supplements be split into smaller doses?
NIH reports that fractional absorption is highest at elemental-calcium doses of about 500 mg or less at one time. [1] Follow the product label or clinician's instructions rather than changing a prescribed regimen yourself.
Does a blood calcium test tell me whether I need a supplement?
Not by itself. Serum calcium is tightly regulated and is not a good reflection of nutritional calcium status. [1] Testing can be medically important for other reasons, but this page does not recommend routine blood testing for product selection.
