Drug interactions
Metformin + Vitamin B12
Severity: Moderate
Metformin and Vitamin B12: moderate 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
Long-term metformin therapy is associated with lower serum vitamin B12 levels and occasionally clinical deficiency, including anemia or neuropathy. The risk rises with higher doses, longer duration and other risk factors such as older age or poor intake.
What this interaction means in plain words
Metformin and Vitamin B12 can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Metformin belongs to Endocrine; Vitamin B12 belongs to Gastrointestinal Tract.
Why it happens
Metformin is thought to impair calcium-dependent ileal absorption of the B12-intrinsic factor complex, though the mechanism is not fully established.
What to do
Measure vitamin B12 periodically in patients on long-term metformin, especially those with anemia or neuropathy. Replace B12 if deficient; metformin can usually be continued.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Vitamin B12
Other interactions of Metformin
Frequently asked questions
Can I take Metformin with Vitamin B12?
MediHelp rates the interaction as moderate. Metformin and Vitamin B12 can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Long-term metformin therapy is associated with lower serum vitamin B12 levels and occasionally clinical deficiency, including anemia or neuropathy. The risk rises with higher doses, longer duration and other risk factors such as older age or poor intake.
How serious is the interaction between Metformin and Vitamin B12?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Measure vitamin B12 periodically in patients on long-term metformin, especially those with anemia or neuropathy. Replace B12 if deficient; metformin can usually be continued.
What other medicines interact with Vitamin B12?
MediHelp also lists interactions of Vitamin B12 with, for example, Chloramphenicol, Dichlorphenamide, Neomycin po. The full list is on the Vitamin B12 page.
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