Overview
Major bone mineral; also critical for muscle contraction and nerve signaling.
- Dairy
- Sardines
- Leafy greens
- Tofu (set with Ca)
- Citrate (no acid required)
- Carbonate (cheap, needs acid)
- Hydroxyapatite
Mechanism of action
Stored as hydroxyapatite in bone; cytosolic Ca²⁺ triggers muscle contraction and exocytosis.
- · Bone mineralization
- · Excitation-contraction coupling
Effects on the body
Organ system effects
Primary mineral component.
Evidence-based benefits
Reduces fracture risk with vitamin D in deficient elderly
Moderate evidencePotential side effects
- · Constipation (carbonate)
- · Kidney stones
- · Possible CV risk with high-dose supplements (debated)
Drug interactions
Safety & non-supplemental interactions
Educational summary — always confirm with your clinician or pharmacist before starting, stopping, or combining with prescription therapy.
- ·Hypercalcemia
- ·Kidney stones (calcium-oxalate)
- ·Hyperparathyroidism
- ·Sarcoidosis
- ·Levothyroxine (4 h apart)
- ·Tetracyclines, fluoroquinolones, bisphosphonates (2 h apart)
- ·Thiazide diuretics (additive hypercalcemia)
- ·Digoxin
Supplement interactions
None listed.
- Iron (same dose)Mutual absorption inhibition.
Dosing & bioavailability
Where to buy
Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.
Scientific evidence (8)
Calcium: pharmacology, clinical evidence, and safety — narrative review
Examine.com Research Team
Curated narrative review of human and preclinical evidence for Calcium, including mechanism, typical dosing, and safety considerations.
Best-supported outcome: Reduces fracture risk with vitamin D in deficient elderly (evidence: moderate). Additional outcomes and limitations summarized in the full profile.
PubMed: Calcium — Reduces fracture risk with vitamin D in deficient elderly
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PubMed: Calcium — randomized controlled trial
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PubMed: Calcium — meta-analysis
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PubMed: Calcium — pharmacokinetics
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PubMed: Calcium — safety adverse events
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PubMed: Calcium — dose response
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Google Scholar: Calcium — clinical evidence
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Cross-database citation index for Calcium as it relates to "clinical evidence".
Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.