Protocols › Calcium

Calcium for bones

Goal: What trials of calcium used to protect the bones of older adults, and how small the effect on fractures was.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 4 Nov 2026
Dose

500 to 1,200 mg of calcium a day with 400 to 800 IU of vitamin D in reviews of fracture trials.[1] The largest trial gave 1,000 mg of calcium with 400 IU of vitamin D.[2]

Form

Calcium carbonate in the largest trial.[2] In a 3-month trial, citrate and carbonate lowered bone turnover to a similar degree.[3]

When to take

With food. Absorption is highest at 500 mg or less at one time.[1]

How long

1 to 7 years.[1] The gain in bone density did not grow after the first year.[4]

What studies found

A 2026 review of 69 trials with 153,902 people found little to no benefit on fractures and falls.[5] The risk ratio was 0.91 for calcium alone and for calcium with vitamin D.[5] In people over 50, bone density rose by 0.7% to 1.8%.[4] In Australian care homes, extra dairy food with 562 mg of calcium and 12 g of protein a day led to 33% fewer fractures in 2 years.[6]

Ask a doctor first

Stomach problems are common.[7] Calcium with vitamin D raised the risk of kidney stones by 17% in the largest trial.[2] Reviews disagree on whether supplements raise heart risk.[8][9] The upper limit for adults is 2,000 to 2,500 mg a day in the US and 2,500 mg in the EU.[1][10]

People who have had kidney stones or take a medicine every day should ask a doctor or pharmacist first.[1]

References

  1. Calcium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  2. Calcium plus vitamin D supplementation and the risk of fractures. Jackson RD, LaCroix AZ, Gass M, Wallace RB, Robbins J, Lewis CE, et al. N Engl J Med, 2006. PMID 16481635
  3. Acute and 3-month effects of microcrystalline hydroxyapatite, calcium citrate and calcium carbonate on serum calcium and markers of bone turnover: a randomised controlled trial in postmenopausal women. Bristow SM, Gamble GD, Stewart A, Horne L, House ME, Aati O, et al. Br J Nutr, 2014. PMID 25274192
  4. Calcium intake and bone mineral density: systematic review and meta-analysis. Tai V, Leung W, Grey A, Reid IR, Bolland MJ BMJ, 2015. PMID 26420598
  5. Calcium, vitamin D, or combined supplementation to prevent fractures and falls: systematic review and meta-analysis. Massé O, Mercurio CM, Dupuis S, Al Sahwi M, Arruda A, Dallaire G, et al. BMJ, 2026. PMID 42161415
  6. Effect of dietary sources of calcium and protein on hip fractures and falls in older adults in residential care: cluster randomised controlled trial. Iuliano S, Poon S, Robbins J, Bui M, Wang X, De Groot L, et al. BMJ, 2021. PMID 34670754
  7. Calcium Supplementation- Efficacy and Safety. Reid IR Curr Osteoporos Rep, 2025. PMID 39937345
  8. Calcium Supplements and Risk of Cardiovascular Disease: A Meta-Analysis of Clinical Trials. Myung SK, Kim HB, Lee YJ, Choi YJ, Oh SW Nutrients, 2021. PMID 33530332
  9. Association Between Calcium Supplementation and the Risk of Cardiovascular Disease and Stroke: A Systematic Review and Meta-Analysis. Sim MG, Teo YN, Teo YH, Syn NL, Li TYW, Yeo LLL, et al. Heart Lung Circ, 2023. PMID 37743221
  10. Scientific Opinion on the Tolerable Upper Intake Level of calcium. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) European Food Safety Authority, 2012. efsa.onlinelibrary.wiley.com