Calcium carbonate/citrate (bone health)

Tier 1 — strong evidence · Bone density · Osteoporosis · Pregnancy

The two dominant supplemental calcium forms differ in when they can be taken and who absorbs them best. Carbonate (40% elemental calcium) is the most concentrated and cheapest form but requires stomach acid for dissolution — best taken with meals; unsuitable for those on PPIs or with achlorhydria. Citrate (21% elemental calcium) dissolves without acid and can be taken any time, making it preferred for adults over 50, bariatric surgery patients, and PPI users. The 2023 Sim RCT meta-analysis (12 trials, PMID 37743221) found calcium supplementation was not significantly associated with MI,…

Dose: 500–600 mg elemental calcium per dose; no more than 500 mg at one time. Target total daily intake 1,000 mg (women 19–50, men 19–70) to 1,200 mg (women 51+, men 71+) from all sources. Always pair with vitamin D3 (1,000–2,000 IU/day).