Protocols › Calcium

Calcium for pre-eclampsia

Goal: What trials of calcium in pregnancy used to prevent pre-eclampsia, and why newer reviews found a smaller effect.

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

The World Health Organization (WHO) recommends 1.5 to 2.0 g a day in populations with low calcium intake.[1] Two trials of 11,000 women each found 500 mg a day not worse than 1,500 mg for pre-eclampsia.[2]

Form

Elemental calcium by mouth.[1]

When to take

The WHO amount is divided into three doses a day.[2]

How long

During pregnancy.[3] One trial that started 500 mg a day before conception made no difference.[4]

What studies found

A 2025 Cochrane review of 10 trials found little to no difference in pre-eclampsia in large trials (risk ratio 0.92, 14,730 women, high certainty).[3] The 2018 version found a risk ratio of 0.45, and it warned that small trials might have inflated the effect.[5] In the 3 largest trials of that earlier analysis, the risk ratio was also 0.92.[6]

Ask a doctor first

The upper limit in pregnancy is 2,500 mg a day from age 19 and 3,000 mg at 14 to 18 years in the US, and 2,500 mg for adults in the EU.[4][7] The 2018 Cochrane review saw more cases of HELLP syndrome with calcium, small in absolute numbers (16 against 6).[5]

Anyone who is pregnant should ask a doctor or midwife first. In the US, pre-eclampsia is a leading cause of serious illness and death in mothers and newborns.[4]

References

  1. Calcium supplementation during pregnancy to reduce the risk of pre-eclampsia. World Health Organization, 2023. www.who.int
  2. Two Randomized Trials of Low-Dose Calcium Supplementation in Pregnancy. Dwarkanath P, Muhihi A, Sudfeld CR, Wylie BJ, Wang M, Perumal N, et al. N Engl J Med, 2024. PMID 38197817
  3. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cluver CA, Rohwer C, Rohwer AC Cochrane Database Syst Rev, 2025. PMID 41330480
  4. Calcium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  5. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Hofmeyr GJ, Lawrie TA, Atallah ÁN, Torloni MR Cochrane Database Syst Rev, 2018. PMID 30277579
  6. Calcium supplementation for the prevention of pre-eclampsia: Challenging the evidence from meta-analyses. Wright D, Wright A, Magee LA, Von Dadelszen P, Nicolaides KH BJOG, 2024. PMID 38302677
  7. 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