NutriStack
Famotidine and Vitamin B12, a caution.
Long-term famotidine therapy can lower vitamin B12 status by reducing acid-pepsin-dependent release of B12 from food. The Kaiser case-control study found that two or more years of H2 blocker use was associated with a 25% higher risk of B12 deficiency. The effect is smaller than with PPIs but real, and matters more in older adults and vegetarians.
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.
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At a glance
- Substances
- Famotidine and Vitamin B12
- 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. Long-term famotidine therapy can lower vitamin B12 status by reducing acid-pepsin-dependent release of B12 from food. The Kaiser case-control study found that two or more years of H2 blocker use was associated with a 25% higher risk of B12 deficiency. The effect is smaller than with PPIs but real, and matters more in older adults and vegetarians.
Mechanism. Famotidine reversibly blocks parietal cell H2 receptors, reducing gastric acid and pepsin secretion. Acid and pepsin are needed to free B12 from dietary protein so that intrinsic factor can bind it for ileal absorption.
Recommendation. If you take famotidine daily for more than two years, ask for a periodic serum B12 check. A daily oral B12 supplement, ideally methylcobalamin, is a reasonable insurance step and does not require gastric acid for absorption.
Sources (2)
- Lam JR, Schneider JL, Zhao W, Corley DA. Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency. JAMA. 2013;310(22):2435-42. PMID 24327038
- Miller JW. Proton Pump Inhibitors, H2-Receptor Antagonists, Metformin, and Vitamin B-12 Deficiency: Clinical Implications. Adv Nutr. 2018;9(4):511S-518S. PMID 30032223
Stack Score
How this pair moves the number.
Effect on the composite score
If both Famotidine and Vitamin B12 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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