Is Magnesium Safe with Calcium carbonate?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Separate calcium carbonate and magnesium supplements by at least 2 hours. Take calcium with meals and magnesium at a different time of day, such as bedtime.
Why this interaction occurs
Calcium and magnesium compete for the same intestinal transport channels (primarily divalent metal transporter-1). High-dose calcium carbonate can significantly reduce magnesium absorption by up to 30-40%, potentially leading to magnesium deficiency over time, which paradoxically impairs bone mineralization.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 914,008 reports mentioning Calcium carbonate. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Calcium carbonate + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Magnesium interactions → · All Calcium carbonate interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.