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Does calcium cause kidney stones?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

NIH says higher intakes of supplemental calcium might increase the risk of kidney stones, based on the Women's Health Initiative, where women taking 1,000 mg of calcium with vitamin D had 17% more stones over 7 years. Two later systematic reviews found no such link, and calcium from food went with fewer stones in one cohort.1,2

Key facts

  • NIH says higher intakes of supplemental calcium might increase the risk of kidney stones, and its upper limits rest on the Women's Health Initiative.1
  • In that randomized trial of 36,282 women, 1,000 mg of calcium with 400 IU of vitamin D a day for about 7 years went with 17% more self-reported stones.2
  • NIH says two later systematic reviews, of 10 studies and of 11 trials, found no such association.1
  • In a cohort of 91,731 women, higher dietary calcium went with fewer stones and supplemental calcium with more, with a relative risk of 1.20.3
  • MedlinePlus says higher calcium amounts over a long period raise the risk for kidney stones in some people.4

What NIH says about calcium and kidney stones

NIH says higher intakes of supplemental calcium might increase the risk of kidney stones. It explains that the upper limits for calcium are based on observational evidence from the Women's Health Initiative linking supplemental calcium at 1,000 mg a day for 7 years to a greater risk of kidney stones, and then adds that two later systematic reviews found no such association.1

In the Women's Health Initiative, 36,282 women taking 1,000 mg of calcium and 400 IU of vitamin D a day had 17% more kidney stones than those on placebo over about 7 years. The upper limit was set on this evidence, although two later reviews of other trials found no such link.1,5

MedlinePlus is more direct. It says that increased calcium for a limited period does not normally cause side effects, but that receiving higher amounts over a long period raises the risk for kidney stones in some people.4

What did the trial and the cohort study find?

In the Women's Health Initiative trial, 36,282 postmenopausal women took 500 mg of calcium carbonate with 200 IU of vitamin D twice a day, or placebo, for an average of 7 years. Self-reported urinary tract stones were more common with calcium and vitamin D, at 449 women against 381, with a hazard ratio of 1.17 (1.02 to 1.34). Total calcium intake and use of calcium supplements at baseline were not associated with stones.2

In the Nurses' Health Study, 91,731 women with no history of stones were followed for 12 years. Higher dietary calcium went with fewer stones, with a relative risk of 0.65 for the highest against the lowest fifth, while supplemental calcium went with more stones, with a relative risk of 1.20 (1.02 to 1.41). The authors suggested that when calcium is taken relative to the oxalate in meals may explain the difference.3

A cohort study shows an association, not cause, and the trial combined calcium with vitamin D, so neither isolates calcium alone.2,3

Did later reviews confirm the trial's finding?

NIH describes two reviews. One covered 10 studies in more than 8,000 adults with osteoporosis who took 120 to 1,500 mg of calcium daily for 3 days to 3 years. The other covered 11 randomized trials in 51,419 adults aged 50 and older who took 1,000 to 1,600 mg of calcium with or without vitamin D for 2 to 7 years. Neither found an association with kidney stones.1

The sources checked do not explain why the trial and the reviews differ, or say how the findings apply to people who have already had a kidney stone, which is why the question belongs with a doctor.1

Does calcium cause constipation, gas, nausea or diarrhea?

Yes for constipation, gas and bloating, according to NIH, which says calcium supplements can cause gas, bloating, constipation or a mix, more often with calcium carbonate than citrate. MedlinePlus lists upset stomach, vomiting, belching and constipation for calcium carbonate as a medicine. Diarrhea is not named in the sources checked.1,6

Calcium supplements can cause gas, bloating, constipation or a mix of these. Carbonate causes them more often than citrate, especially in older adults with less stomach acid; smaller doses spread through the day, taking it with meals or switching forms can help.1,7

High blood calcium is rare in healthy people and usually comes from conditions such as overactive parathyroid glands or cancer rather than diet. It can cause poor muscle tone, kidney problems, constipation, nausea, weight loss, tiredness, frequent urination and abnormal heart rhythms.1,7

Who should ask a doctor about calcium and kidney stones

  • Anyone who has had kidney stones, or has kidney disease, who should ask their doctor before taking calcium supplements.1
  • Anyone who has been told they have high blood calcium or a parathyroid condition.1
  • Anyone who takes calcium and vitamin D together every day for years, who should ask about the amount.2
  • Anyone with heart disease or at high risk of it, since NIH describes the research on calcium supplements and the heart as mixed.1

Questions people ask

Does calcium cause kidney stones?

NIH says higher intakes of supplemental calcium might increase the risk of kidney stones, but that two later systematic reviews found no such association. Ask your doctor, especially if you have had stones.1

Does calcium cause constipation?

NIH says calcium supplements can cause gas, bloating and constipation, more often with carbonate than citrate. Smaller doses spread through the day, meals or a different form can help.1,7

Does calcium cause diarrhea?

The sources checked name gas, bloating and constipation, and do not name diarrhea for calcium supplements. Ask your doctor or pharmacist if you have diarrhea after starting a supplement.1,7

Does calcium cause high blood pressure?

The sources checked do not report calcium supplements raising blood pressure. NIH describes mixed research on calcium supplements and the heart, and says an expert panel judged intakes within the upper limit neither raise nor lower heart risk.1

Does calcium cause weight gain?

NIH describes a review of 41 trials in 4,802 adults that found calcium supplements had no effect on body weight or body fat. Ask your doctor if you notice other changes.1

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Sources

  1. Office of Dietary Supplements, National Institutes of Health. Calcium: Fact Sheet for Health Professionals. Updated June 22, 2026. Opened 2026-10-07.
  2. Wallace RB, Wactawski-Wende J, O'Sullivan MJ, Larson JC, Cochrane B, Gass M, et al. Urinary tract stone occurrence in the Women's Health Initiative (WHI) randomized clinical trial of calcium and vitamin D supplements. Am J Clin Nutr. 2011;94(1):270-7. A randomized, placebo-controlled trial in 36,282 women. Opened 2026-10-11.
  3. Curhan GC, Willett WC, Speizer FE, Spiegelman D, Stampfer MJ. Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. Ann Intern Med. 1997;126(7):497-504. A prospective cohort study of 91,731 women. Opened 2026-10-11.
  4. MedlinePlus Medical Encyclopedia. Calcium in diet. U.S. National Library of Medicine. Review date 1/21/2025. Opened 2026-10-11.
  5. Jackson RD, LaCroix AZ, Gass M, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med. 2006;354(7):669-683. Opened 2026-10-07.
  6. MedlinePlus, U.S. National Library of Medicine. Calcium Carbonate: MedlinePlus Drug Information. Last revised June 20, 2024. Opened 2026-10-07.
  7. Office of Dietary Supplements, National Institutes of Health. Calcium: Fact Sheet for Consumers. Updated September 14, 2023. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.