Drug interactions
Cimetidine + Cyanocobalamin
Severity: Minor
Cimetidine and Cyanocobalamin: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Reduced gastric acid from cimetidine impairs release of protein-bound vitamin B12 from food, and long-term use may contribute to lower B12 levels. Crystalline oral cyanocobalamin is less affected, so the effect is small in most patients.
What this interaction means in plain words
Cimetidine and Cyanocobalamin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Cimetidine belongs to Gastrointestinal Tract; Cyanocobalamin belongs to Miscellaneous.
Why it happens
Cimetidine suppresses gastric acid and thereby reduces dietary B12 absorption.
What to do
In long-term cimetidine users, especially older adults or those with other risk factors, check B12 status periodically and supplement if low.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Cimetidine
- Cimetidine + Dofetilide Contraindicated
- Cimetidine + Fezolinetant Contraindicated
- Alfentanil + Cimetidine Major
- Atazanavir + Cimetidine Major
- Carmustine + Cimetidine Major
- Cimetidine + Citalopram Major
Other interactions of Cyanocobalamin
Frequently asked questions
Can I take Cimetidine with Cyanocobalamin?
MediHelp rates the interaction as minor. Cimetidine and Cyanocobalamin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Reduced gastric acid from cimetidine impairs release of protein-bound vitamin B12 from food, and long-term use may contribute to lower B12 levels. Crystalline oral cyanocobalamin is less affected, so the effect is small in most patients.
How serious is the interaction between Cimetidine and Cyanocobalamin?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: In long-term cimetidine users, especially older adults or those with other risk factors, check B12 status periodically and supplement if low.
What other medicines interact with Cimetidine?
MediHelp also lists interactions of Cimetidine with, for example, Dofetilide, Fezolinetant, Alfentanil. The full list is on the Cimetidine page.
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