NutriStack
Iron and Omeprazole, a caution.
Omeprazole reduces gastric acid production, which is essential for converting dietary and supplemental iron to its absorbable ferrous (Fe2+) form. Long-term PPI use can lead to iron deficiency, particularly in patients with marginal iron stores or those relying on non-heme iron sources.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Iron and Omeprazole
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 6 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. Omeprazole reduces gastric acid production, which is essential for converting dietary and supplemental iron to its absorbable ferrous (Fe2+) form. Long-term PPI use can lead to iron deficiency, particularly in patients with marginal iron stores or those relying on non-heme iron sources.
Mechanism. Gastric acid is required to reduce ferric iron (Fe3+) to ferrous iron (Fe2+) for absorption by DMT1 in the duodenum. Omeprazole raises gastric pH to >4, significantly impairing this reduction step and reducing non-heme iron bioavailability.
Recommendation. If on long-term omeprazole, monitor iron levels and ferritin periodically. Consider taking iron supplements with vitamin C to enhance absorption, or use ferrous bisglycinate which is less pH-dependent. Take iron between meals if tolerated.
Sources (6)
- Sarzynski E et al. Association between proton pump inhibitor use and anemia: a retrospective cohort study. Dig Dis Sci. 2011;56(8):2349-2353. PMID 21318590
- Choudhury A, Jena A, Jearth V, Dutta AK et al.. Vitamin B12 deficiency and use of proton pump inhibitors: a systematic review and meta-analysis. Expert Review of Gastroenterology & Hepatology. 2023. PMID 37060552
- Fischer JAJ, Cherian AM, Bone JN, Karakochuk CD. The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. 2023. PMID 36728680
- Rehman T, Agrawal R, Ahamed F et al.. Optimal dose and duration of iron supplementation for treating iron deficiency anaemia in children and adolescents: A systematic review and meta-analysis. PLoS One. 2025. PMID 39951396
- Gutema BT, Sorrie MB, Megersa ND et al.. Effects of iron supplementation on cognitive development in school-age children: Systematic review and meta-analysis. PLoS One. 2023. PMID 37368919
- Hansen R, Sejer EPF, Holm C, Schroll JB. Iron supplements in pregnant women with normal iron status: A systematic review and meta-analysis. Acta Obstetricia et Gynecologica Scandinavica. 2023. PMID 37403900
Stack Score
How this pair moves the number.
Effect on the composite score
If both Iron and Omeprazole are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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