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ingestible · for pms & menstrual health

Calcium Carbonate

Reviewed by the Nimbera editorial team · Last updated May 2026

Thys-Jacobs et al. 1998 Am J Obstet Gynecol (PMID 9731851) - Double-blind, placebo-controlled multicenter RCT found 1200 mg/day calcium carbonate produced a 48% reduction in total PMS symptom scores from baseline by the third treatment cycle vs. 30% reduction with placebo; all four symptom factors (negative affect, water retention, food cravings, pain) were significantly improved.$8-15 per month

How to use

Take 600 mg of calcium carbonate twice daily (total 1200 mg/day) with food - calcium is absorbed best in doses under 500-600 mg at a time. Take one dose with lunch and one with dinner. Calcium carbonate requires stomach acid for absorption so take with meals. Continue daily throughout the month.

How it works

Calcium plays a central role in smooth muscle contraction, neurotransmitter release, and intracellular signaling. Fluctuating estrogen levels during the menstrual cycle affect calcium regulation and parathyroid hormone, contributing to PMS symptoms. Supplemental calcium may stabilize the intracellular calcium environment, reducing neuromuscular irritability, mood fluctuations, and cramping.

Where to buy

Caltrate 600 mg calcium carbonate tablets ($10-$15/120 tabs), Tums Ultra 1000 ($8-$12/72 tabs, doubles as antacid), Nature Made Calcium 500 mg ($10-$14/130 tabs). Available at any pharmacy, Walmart, Target, Costco.

Typical cost: $8-15 per month

Safety notes

Do not exceed 2500 mg total calcium daily from all sources (food plus supplements) - excess calcium increases risk of kidney stones. Calcium carbonate can cause constipation or bloating in some women; calcium citrate is gentler if this occurs. Calcium competes with iron absorption - space iron supplements 2 hours apart. May reduce absorption of thyroid hormone, bisphosphonates, and some antibiotics - take 2 hours apart.

Drug & supplement interactions

  • Always tell your doctor or pharmacist about any supplements you take.
  • Interactions can occur with prescription medications, blood thinners, and immunosuppressants.
  • Herbal remedies can affect how the body absorbs or metabolises drugs.
  • Check drugs.com interactions checker before starting.

Clinical source

Thys-Jacobs et al. 1998 - Am J Obstet Gynecol (PMID 9731851)

This information is compiled from primary clinical literature and is for informational purposes only. It is not a substitute for professional medical advice. Read our full disclaimer.