NutriStack
Famotidine and Iron, a caution.
Famotidine can reduce absorption of oral iron, especially non-heme iron salts that require gastric acid. In the Kaiser study, two or more years of H2 blocker use was associated with about a 1.6-fold increase in iron deficiency risk. The effect is smaller than with PPIs but still clinically relevant in patients with menstrual or GI losses.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
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
- Famotidine and Iron
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 2 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. Famotidine can reduce absorption of oral iron, especially non-heme iron salts that require gastric acid. In the Kaiser study, two or more years of H2 blocker use was associated with about a 1.6-fold increase in iron deficiency risk. The effect is smaller than with PPIs but still clinically relevant in patients with menstrual or GI losses.
Mechanism. Gastric acid reduces ferric to ferrous iron and solubilizes iron salts for duodenal absorption by DMT1. Famotidine-induced reduction in gastric acid output (typically 60-80%) blunts both steps.
Recommendation. Take iron supplements at least 2-4 hours apart from famotidine. Iron bisglycinate or a heme-iron product is less acid-dependent. Recheck ferritin 3 months after starting iron repletion.
Minimum separation. 120
Sources (2)
- Lam JR, Schneider JL, Quesenberry CP, Corley DA. Proton Pump Inhibitor and Histamine-2 Receptor Antagonist Use and Iron Deficiency. Gastroenterology. 2017;152(4):821-9. PMID 27890768
- Freedberg DE, Kim LS, Yang YX. The Risks and Benefits of Long-term Use of Proton Pump Inhibitors: Expert Review and Best Practice Advice From the American Gastroenterological Association. Gastroenterology. 2017;152(4):706-15. PMID 28257716
Stack Score
How this pair moves the number.
Effect on the composite score
If both Famotidine and Iron 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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