NutriStack
Cimetidine and Methylcobalamin, a synergy.
Methylcobalamin (a free coenzyme form of B12) does not need gastric acid or pepsin to be released from food protein, making it a more reliable B12 source for patients on cimetidine. Two or more years of H2 blocker use is linked to roughly 25% higher B12 deficiency risk, and oral methylcobalamin can prevent that deficit in most patients.
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
- Cimetidine and Methylcobalamin
- Pair type
- Synergy
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- +2 to your Stack Score (per scored synergy row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Synergy · Moderate evidence
Synergy
What is happening. Methylcobalamin (a free coenzyme form of B12) does not need gastric acid or pepsin to be released from food protein, making it a more reliable B12 source for patients on cimetidine. Two or more years of H2 blocker use is linked to roughly 25% higher B12 deficiency risk, and oral methylcobalamin can prevent that deficit in most patients.
Mechanism. Free B12 supplements bypass the acid-pepsin step needed to liberate cobalamin from dietary protein. Intrinsic factor binds the free vitamin directly for ileal absorption, which remains intact on H2 blockers.
Recommendation. If you take cimetidine long-term, 500-1000 mcg of oral methylcobalamin daily is a sensible insurance dose. Recheck serum B12 yearly while on chronic cimetidine.
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 Cimetidine and Methylcobalamin are in the same stack, this pair applies +2 to your Stack Score (per scored synergy row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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