Calcium Carbonate

Most common and economical form of calcium supplement with highest elemental calcium content, requiring stomach acid for optimal absorption

Scientific nameCalcium Carbonate FormulaCaCO3 Molecular weight100.09 g/mol CAS471-34-1

25 absorption score

7 safety / 10

10 USD per month

40 elemental calcium %

6 documented interactions

Check it against something

Evidence level A

Calcium Carbonate with:

76 out of 100

Needs attention Separate by 2-4 hours to avoid the interaction below.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Highest elemental calcium content

Contains 40% elemental calcium, more than any other form

Simple carbonate structure provides maximum calcium per gram Evidence A-grade Per dose benefit

Cost-effective bone health support

Most affordable way to supplement with calcium

High elemental content reduces cost per mg of calcium Evidence A-grade Economic benefit

Antacid properties

Neutralizes stomach acid providing heartburn relief

Carbonate neutralizes gastric acid on contact Evidence A-grade 15-30 minutes

Bone density support

Helps maintain and build bone mineral density

Provides essential calcium for bone mineralization Evidence A-grade 6-12 months

Teeth health protection

Supports dental health and enamel strength

Calcium essential for tooth structure and remineralization Evidence A-grade 3-6 months

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Calcium Bone health & muscle function 1,000-1,200 mg A 30% Turmeric Anti-inflammatory & antioxidant 300-1000mg A 3% Vitamin D3 Bone health & immune support 1000-2000 IU A 85% Collagen Peptides Skin health & joint support 5-15g B 85% Phosphorus Bone health & energy metabolism 700-1250mg A 80% Bone Broth Collagen Gut healing & collagen support 20-40g powder B 85%

Or a different form of the same thing

the comparison people search most

Calcium Carbonate vs Calcium absorption 25 against 30 · $10 against $20 a month 30% Calcium Carbonate vs Calcium Citrate absorption 25 against 45 · $10 against $20 a month 45% Calcium Carbonate vs Calcium Hydroxyapatite absorption 25 against 40 · $10 against $60 a month 40%

All Calcium forms ranked by absorption →

Every pair we checked

12 combinations scored by the engine

Calcium Carbonate + Caffeine High intake increases calcium excretion Needs attention 58

Calcium Carbonate + Whey Protein Very high calcium may interfere with protein absorption Needs attention 61

Calcium Carbonate + Creatine Monohydrate No documented interaction either way No known interaction 70

Calcium Carbonate + Bovine Collagen No documented interaction either way No known interaction 70

Calcium Carbonate + DHA No documented interaction either way No known interaction 70

Calcium Carbonate + Turmeric No documented interaction either way No known interaction 70

Calcium Carbonate + Fish Oil (EPA/DHA) No documented interaction either way No known interaction 70

Calcium Carbonate + Marine Collagen No documented interaction either way No known interaction 70

Calcium Carbonate + Vitamin D3 Reduces vitamin D conversion efficiency Needs attention 76

Calcium Carbonate + Magnesium Oxide High calcium can interfere with magnesium absorption Needs attention 76

Calcium Carbonate + Lactase Enhanced calcium absorption from dairy sources Works better together 82

Calcium Carbonate + Vitamin C (Ascorbic Acid) Essential for calcium absorption and utilization Works better together 94

Dosage

With meals divided doses

Daily1000-1200 mg

Maintenance500-1000 mg daily

Therapeutic1000-1500 mg daily

Bone health1000-1200 mg daily (divided)

Elemental calciumContains ~40% elemental calcium

Upper limit 2500 mg NIH ODS

Before you take it

VeganYes

When to expect it

First Effects15-30 minutes for antacid effects, weeks for bone benefits

Peak Benefits6-12 months for optimal bone density improvements

Deficiency DevelopmentMonths to years with inadequate intake

Toxicity OnsetRare with normal intake, possible with excessive supplementation

How to measure it

$40-100

MarkerSerum calcium, ionized calcium, 24-hour urine calcium

OptimalSerum: 8.5-10.5 mg/dL, Ionized: 4.5-5.3 mg/dL

Deficient belowSerum: <8.5 mg/dL

FrequencyAnnually or as directed by healthcare provider

What people actually reported to the FDA

CAERS, 569 reports naming it as the suspect

Most reported effects

Dyspnoea 58

Vomiting 33

Excluded from the list above: choking (207), dysphagia (71), foreign body trauma (54), foreign body (33). Those are people struggling with the tablet itself, not with the compound.

Named as the suspect 569 reports of 1,000+ that mention it at all

Serious outcome 89% hospitalisation, emergency room or worse

Other Serious or Important Medical Event468

Hospitalization82

Visited a Health Care Provider63

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

What actually reaches you

The label counts the carrier, your body does not

Elemental calcium 40% of 100.09 g/mol

Absorption Low 25 of 100 · poorly absorbed relative to other forms

Measured 22% of the dose PubMed 2273192

Reaches blood daily 96.8 mg

Cost per 100 mg absorbed $0.34 vs $10/month on the label

A 500 mg capsule of Calcium Carbonate contains 200 mg of calcium. At the measured 22% absorption that is about 44 mg reaching your blood. How this is calculated →

Works better with

3 documented

Vitamin D

Essential for calcium absorption and utilization

Vitamin D increases calcium absorption in intestines · level A

Magnesium

Required for proper calcium metabolism

Magnesium cofactor for calcium-dependent enzymes · level A

Vitamin K2

Directs calcium to bones rather than soft tissues

K2 activates proteins that regulate calcium deposition · level A

What not to take with Calcium Carbonate

3 documented

Iron Zinc Magnesium

Calcium reduces absorption of these minerals

Competition for absorption transporters · moderate significance

Fiber Phytates

Dietary fiber and phytates can bind calcium

Chelation reduces bioavailability · moderate significance

Caffeine Sodium

High intake increases calcium excretion

Enhanced urinary calcium loss · mild significance

Medication interactions

Discuss these with a pharmacist before combining

tetracycline-quinolone-antibiotics Major

Calcium severely reduces antibiotic absorption

What to do: Space doses 2-4 hours apart

levothyroxine Major

Reduces thyroid hormone absorption

What to do: Take thyroid medication 4 hours before calcium

bisphosphonates Major

Significantly reduces bisphosphonate absorption

What to do: Take bisphosphonate 2+ hours before calcium

thiazide-diuretics Moderate

May increase risk of hypercalcemia

What to do: Monitor calcium levels regularly

Available forms

bioavailability compared

Ranks 4 of 4 among calcium forms. Calcium Citrate absorbs better — 45%. Compare all forms →

Calcium Carbonate (Tablets/Chewables) 25

Calcium Carbonate (Tablets/Chewables): Highest elemental Ca, Lowest cost, Antacid effect, Most research

Food sources

before you supplement

Dairy products 300mg per cup milk · 30

Fortified plant milks 300mg per cup (fortified) · 25

Sardines with bones 325mg per 3.75 oz can · 35

Dark leafy greens 200mg per cup cooked · 50

Too little

deficiency signs

Bone loss and osteoporosis
Dental problems and tooth decay
Muscle cramps and spasms
Tingling in fingers and toes
Brittle or soft nails
Increased fracture risk
Growth retardation in children

Too much

toxicity signs

Kidney stones (calcium oxalate)
Constipation and digestive upset
Reduced absorption of other minerals
Hypercalcemia (rare with supplements)
Interference with heart medications

Who benefits most

budget-conscious-bone-health

Most affordable way to supplement with calcium

500-600 mg twice daily with meals

postmenopausal-women

High calcium needs for bone loss prevention

600 mg twice daily with vitamin D

adequate-stomach-acid

Best form for those with normal gastric acid production

500 mg twice daily with meals

antacid-users

Dual benefit of calcium supplementation and acid neutralization

500-1000 mg as needed for heartburn

basic-supplementation

Simple, proven calcium supplementation

500-1000 mg daily with food

Where to buy it

compare forms first

Look for Calcium Carbonate at 1000-1200 mg per serving. The form that matters here is Calcium Carbonate (Tablets/Chewables).

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What else affects it

Beyond other supplements

Fiber phytates

Dietary fiber and phytates can bind calcium

Chelation reduces bioavailability

Caffeine sodium

High intake increases calcium excretion

Enhanced urinary calcium loss

How it works

Requires gastric acid for dissolution into ionic calcium
Absorbed primarily in duodenum via active transport
Competes with other minerals for absorption pathways
Carbonate component neutralizes stomach acid
Absorption decreases as dose size increases
Vitamin D enhances calcium absorption efficiency

Key findings

what the evidence supports

Most extensively studied calcium form for bone health
Effective for reducing fracture risk when combined with vitamin D
Lower bioavailability than citrate but still effective for bone health
Cost-effective option for meeting daily calcium requirements

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Calcium Carbonate?

Documented effects: Highest elemental calcium content; Cost-effective bone health support; Antacid properties; Bone density support. Contains 40% elemental calcium, more than any other form

How much Calcium Carbonate should you take per day?

The common daily range is 1000-1200 mg. By goal — maintenance: 500-1000 mg daily; therapeutic: 1000-1500 mg daily; bone health: 1000-1200 mg daily (divided); elemental calcium: Contains ~40% elemental calcium.

When is the best time to take Calcium Carbonate?

With meals divided doses. First effects are typically reported within 15-30 minutes for antacid effects, weeks for bone benefits.

What are the side effects of Calcium Carbonate?

At excessive doses: Kidney stones (calcium oxalate), Constipation and digestive upset, Reduced absorption of other minerals, Hypercalcemia (rare with supplements), Interference with heart medications. Safety rating at normal doses is 7 out of 10.

What should you not take with Calcium Carbonate?

Separate it from Iron Zinc Magnesium, Fiber Phytates, Caffeine Sodium by two to four hours. Calcium reduces absorption of these minerals

Does Calcium Carbonate interact with medications?

Documented interactions with tetracycline-quinolone-antibiotics, levothyroxine, bisphosphonates, thiazide-diuretics. Discuss these with a pharmacist before combining.

How much Calcium Carbonate is too much?

The tolerable upper intake level is 2500 mg per day for adults, per NIH ODS. Above that, the risk of adverse effects rises: Kidney stones (calcium oxalate), Constipation and digestive upset, Reduced absorption of other minerals.

How do you know if you need Calcium Carbonate?

The marker is Serum calcium, ionized calcium, 24-hour urine calcium, optimal range Serum: 8.5-10.5 mg/dL, Ionized: 4.5-5.3 mg/dL. Common deficiency signs: Bone loss and osteoporosis, Dental problems and tooth decay, Muscle cramps and spasms, Tingling in fingers and toes.

Taken for

38 Joints & Bones

Vitamin D3 · Calcium Carbonate · Bovine Collagen