Is Calcium supplement Safe with Iron supplement?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Take iron and calcium supplements at least 2 hours apart. Take iron on an empty stomach or with vitamin C to enhance absorption. Do not take them simultaneously.
Why this interaction occurs
Calcium directly inhibits both heme and non-heme iron absorption in the duodenum by competing for shared divalent metal transporter-1 (DMT-1) pathways. Even a single dose of 300–600 mg calcium can reduce iron absorption by 30–50%.
Evidence
Evidence level: strong.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 136,322 reports mentioning Iron supplement. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Iron supplement + 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 Calcium supplement interactions → · All Iron supplement interactions →
Already checked this one — check your whole list
Educational only — not medical advice.
Always confirm with your doctor or pharmacist.