Drug interactions
calcium (oral) + iron (oral)
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Calcium salts reduce GI absorption of oral iron, potentially diminishing hematologic response when taken together.
Mechanism of action
Formation of insoluble complexes and inhibition/competition at intestinal transporters → decreased iron bioavailability.
Clinical management
Avoid coadministration; separate iron and calcium by at least 2 hours (preferably 2–4 hours). Take iron on an empty stomach or with vitamin C. Monitor Hgb, ferritin, and response; adjust therapy if inadequate.
References
- Calcium Salts—Drug Interactions (calcium salts may decrease absorption of iron salts) — Lexicomp
- Oral iron therapy in adults — UpToDate
- Calcium carbonate and ferrous sulfate Interactions — Drugs.com
Frequently asked questions
Can I take calcium (oral) with iron (oral)?
The interaction is rated: Moderate. Calcium salts reduce GI absorption of oral iron, potentially diminishing hematologic response when taken together.
How serious is the interaction between calcium (oral) and iron (oral)?
The interaction is rated: Moderate. Evidence level: High.
How is the interaction between calcium (oral) and iron (oral) managed?
Avoid coadministration; separate iron and calcium by at least 2 hours (preferably 2–4 hours). Take iron on an empty stomach or with vitamin C. Monitor Hgb, ferritin, and response; adjust therapy if inadequate.
Why do calcium (oral) and iron (oral) interact?
Formation of insoluble complexes and inhibition/competition at intestinal transporters → decreased iron bioavailability.
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