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Calcium Side Effects & Safety

Evidence:Strong
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Safe with Caution

Potential Side Effects

  • Constipation (most common, especially with calcium carbonate)
  • Bloating and gas
  • Potential increased cardiovascular risk at high supplemental doses (>1,000mg/day) — controversial, debated in literature
  • Kidney stone risk may increase with high-dose supplements without adequate hydration

Drug & Supplement Interactions

  • Reduces absorption of thyroid medications (levothyroxine) — separate by 4 hours
  • Reduces absorption of bisphosphonates — separate by 2 hours
  • Reduces absorption of tetracycline and quinolone antibiotics
  • Competes with iron, zinc, and magnesium for absorption — take at different times
  • Vitamin D enhances calcium absorption — always co-supplement

Maximum Dose

Do not exceed: 2,500mg/day total from all sources (NIH UL); do not exceed 500-600mg per dose for optimal absorption

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References

  1. Jackson RD, LaCroix AZ, Gass M, et al. (2006). Calcium plus vitamin D supplementation and the risk of fractures. New England Journal of Medicine. DOI PubMed
  2. Meta-analysisBolland MJ, Leung W, Tai V, et al. (2015). Calcium intake and risk of fracture: systematic review. BMJ. DOI PubMed
  3. Meta-analysisTai V, Leung W, Grey A, Reid IR, Bolland MJ (2015). Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ. DOI PubMed
  4. Yong Y, Giovannucci J, Pang SN, Hong W, et al. (2025). Coronary Artery Calcium Density and Risk of Cardiovascular Events: A Systematic Review and Meta-Analysis.. JACC. Cardiovascular imaging. DOI PubMed
  5. Sabeti MA, Karimpourtalebi N, Shahravan A, Dianat O (2024). Clinical and Radiographic Failure of Nonsurgical Endodontic Treatment and Retreatment Using Single-cone Technique With Calcium Silicate-based Sealers: A Systematic Review and Meta-analysis.. Journal of endodontics. DOI PubMed
  6. Sunlakawit C, Chaimanakarn C, Srimaneekarn N, Osiri S (2024). Effect of Calcium Hydroxide as an Intracanal Medication on Dentine Fracture Resistance: A Systematic Review and Network Meta-Analysis.. Journal of endodontics. DOI PubMed
  7. Meta-analysisTan L, He R, Zheng X (2024). Effect of vitamin D, calcium, or combined supplementation on fall prevention: a systematic review and updated network meta-analysis.. BMC geriatrics. DOI PubMed
Show 5 more references
  1. Bickelmann FV, Leitzmann MF, Keller M, Baurecht H, et al. (2023). Calcium intake in vegan and vegetarian diets: A systematic review and Meta-analysis.. Critical reviews in food science and nutrition. DOI PubMed
  2. Meta-analysisManoj P, Derwin R, George S (2023). What is the impact of daily oral supplementation of vitamin D3 (cholecalciferol) plus calcium on the incidence of hip fracture in older people? A systematic review and meta-analysis.. International journal of older people nursing. DOI PubMed
  3. Liang L, Kung JY, Mitchelmore B, Cave A, et al. (2022). Comparative peripheral edema for dihydropyridines calcium channel blockers treatment: A systematic review and network meta-analysis.. Journal of clinical hypertension (Greenwich, Conn.). DOI PubMed
  4. Ma Y, Yang L, Luo X, et al. (2024). Clinical efficacy of low-dose aspirin combined with calcium in preventing preeclampsia: A systematic review and meta-analysis.. Pregnancy hypertension. DOI PubMed
  5. Hofmeyr GJ, Manyame S, Medley N, Williams MJ (2022). Calcium for pre-eclampsia prevention: A systematic review and network meta-analysis.. The Cochrane database of systematic reviews. DOI PubMed