Calcium

Calcium supplementation · Calcium Carbonate · Calcium Citrate · Calcium Citrate Malate

Snapshot

Indications	Contraindications
Postmenopausal bone loss¹ Hip fracture risk² Preeclampsia prevention³ Post-thyroidectomy hypocalcemia⁴ Metabolic syndrome risk^5–7	Hypercalcemia⁸ Hypophosphatemia⁸ Hyperparathyroidism⁸

Calcium is the most abundant mineral in the body, forming bone and teeth and mediating muscle, nerve, and clotting function¹. It is absorbed through a vitamin D-dependent pathway, and supplementation fills gaps when diet falls short. Postmenopausal women and people who avoid dairy are most likely to have inadequate intake¹.

Fracture evidence is split: a narrative review of recent meta-analyses reported fewer hip fractures with combined calcium and vitamin D², while other meta-analyses found no effect on hip or total fracture¹. For preeclampsia, a 2025 Cochrane review found little to no difference versus placebo⁹. In a 2026 commentary, the authors argued that the review's trial trustworthiness exclusions were applied inconsistently¹⁰. Products in the National Institutes of Health label database list calcium, mostly as carbonate or citrate; see Form comparison¹.

The tolerable upper intake level rests on kidney stone risk in women¹. Per United States (US) product labeling summarized in the National Institutes of Health fact sheet, levothyroxine is not taken within 4 hours of calcium carbonate, and dolutegravir and quinolone antibiotics are timed apart from calcium¹.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

82 sources, 73 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources