Antacids significantly reduce iron absorption
Iron requires stomach acid for conversion to absorbable Fe2+ form. PPIs and H2 blockers can reduce iron absorption by 65-75%, potentially causing iron deficiency.
Take iron supplements separately from antacids. Consider heme iron sources.
Take iron 2+ hours before antacids, ideally with vitamin C
Antacids significantly reduce iron absorption. Take iron supplements separately from antacids. Consider heme iron sources.
Take iron 2+ hours before antacids, ideally with vitamin C
This interaction is rated “Caution” by Formulate. Iron requires stomach acid for conversion to absorbable Fe2+ form. PPIs and H2 blockers can reduce iron absorption by 65-75%, potentially causing iron deficiency.
Studies from our registry that mention antacids or iron. Each links to the primary source and the other Formulate pages citing it.
Mentions iron · 2017
Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women
Stoffel NU, Cercamondi CI, Brittenham G, et al. · Blood
Landmark absorption study showing iron supplements taken daily (or twice-daily) trigger hepcidin elevation that blocks subsequent absorption — supporting alternate-day dosing as more efficient for iron repletion.
Mentions iron · 2010
Iron bioavailability and dietary reference values
Hurrell R, Egli I · American Journal of Clinical Nutrition
Reviews enhancers (vitamin C, meat) and inhibitors (phytate, polyphenols, calcium) of non-heme iron absorption, providing the mechanistic basis for pairing iron with vitamin C and separating it from tea/coffee.
Mentions iron · 2000
Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability
Hallberg and Hulthén · American Journal of Clinical Nutrition
Foundational model for non-heme iron absorption factoring vitamin C, phytates, tannins, and calcium interactions.
Other interactions to know
Calcium significantly reduces iron absorption
Long-term antacid use depletes B12
Iron reduces levothyroxine absorption
Fluoroquinolones and tetracyclines chelate iron
Zinc and iron compete for absorption
PPIs impair magnesium absorption
PPIs reduce non-heme iron absorption
Phytates in fiber reduce non-heme iron absorption
Check your full stack in the free interaction checker.
The free checker lets you add any combination of supplements and medications at once. The free web app goes further — every stack change surfaces interaction alerts automatically.
Medical disclaimer. This page is for educational purposes only and does not replace advice from a qualified healthcare provider.
Last medically reviewed: