Can You Take Calcium and Iron Together?
Same day is fine; take separate calcium and iron supplements at different times.
The short answer
Taking calcium and iron together may reduce iron absorption, but studies have not reached a clear conclusion about the long-term effect.
Why it happens
Some single-dose studies found lower iron absorption when calcium was taken at the same time. Studies of everyday diets over longer periods have found mixed results.
What to do
If your calcium and iron are separate supplements, take them at different times of day. If you are treating iron deficiency, follow your doctor, pharmacist, or product instructions.
When this advice applies
This advice applies mainly to separate calcium and iron supplements. It should not be applied to every food or multivitamin.
References
- Iron — Health Professional Fact SheetNIH Office of Dietary Supplements · 2025
- Calcium from milk or calcium-fortified foods does not inhibit nonheme-iron absorption from a whole diet consumed over a 4-d periodAmerican Journal of Clinical Nutrition / PubMed · 2004
Updated July 31, 2026 · How to use this guidance