Drug interactions
Cimetidine + Vitamin B12
Severity: Minor
Cimetidine and Vitamin B12: 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
Cimetidine reduces gastric acid, which lowers release of B12 from food proteins and may lower absorption with long-term use. Absorption of crystalline oral B12 is less affected, so clinical deficiency is uncommon.
What this interaction means in plain words
Cimetidine and Vitamin B12 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; Vitamin B12 belongs to Gastrointestinal Tract.
Why it happens
Reduced gastric acid secretion impairs liberation of protein-bound dietary B12.
What to do
Monitor B12 status in long-term users, especially older adults or those with other risk factors. Supplement if levels are 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 Vitamin B12
- Chloramphenicol + Vitamin B12 Moderate
- Dichlorphenamide + Vitamin B12 Moderate
- Metformin + Vitamin B12 Moderate
- Neomycin po + Vitamin B12 Moderate
- Aspirin / citric acid / sodium bicarbonate + Vitamin B12 Minor
- Aspirin + Vitamin B12 Minor
Other interactions of Cimetidine
- Cimetidine + Dofetilide Contraindicated
- Cimetidine + Fezolinetant Contraindicated
- Alfentanil + Cimetidine Major
- Atazanavir + Cimetidine Major
- Carmustine + Cimetidine Major
- Cimetidine + Citalopram Major
Frequently asked questions
Can I take Cimetidine with Vitamin B12?
MediHelp rates the interaction as minor. Cimetidine and Vitamin B12 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 reduces gastric acid, which lowers release of B12 from food proteins and may lower absorption with long-term use. Absorption of crystalline oral B12 is less affected, so clinical deficiency is uncommon.
How serious is the interaction between Cimetidine and Vitamin B12?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor B12 status in long-term users, especially older adults or those with other risk factors. Supplement if levels are low.
What other medicines interact with Vitamin B12?
MediHelp also lists interactions of Vitamin B12 with, for example, Chloramphenicol, Dichlorphenamide, Metformin. The full list is on the Vitamin B12 page.
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