Drug interactions
Metformin + Vitamin b3
Severity: Moderate
Metformin and Vitamin b3: 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
High-dose niacin can raise blood glucose and worsen glycemic control in people with diabetes. This may offset the effect of metformin and necessitate a change in antidiabetic therapy.
What this interaction means in plain words
Metformin and Vitamin b3 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 b3 belongs to Gastrointestinal Tract.
Why it happens
Niacin causes insulin resistance and increased hepatic glucose production, opposing the glucose-lowering effect of metformin.
What to do
Monitor fasting glucose and HbA1c when niacin is started or its dose is changed, and adjust the metformin dose or add therapy if needed. Watch for hypoglycemia if niacin is later stopped.
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 b3
- Lovastatin + Vitamin b3 Major
- Simvastatin + Vitamin b3 Major
- Atorvastatin + Vitamin b3 Moderate
- Cholestyramine + Vitamin b3 Moderate
- Colestipol + Vitamin b3 Moderate
- Fluvastatin + Vitamin b3 Moderate
Other interactions of Metformin
Frequently asked questions
Can I take Metformin with Vitamin b3?
MediHelp rates the interaction as moderate. Metformin and Vitamin b3 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. High-dose niacin can raise blood glucose and worsen glycemic control in people with diabetes. This may offset the effect of metformin and necessitate a change in antidiabetic therapy.
How serious is the interaction between Metformin and Vitamin b3?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor fasting glucose and HbA1c when niacin is started or its dose is changed, and adjust the metformin dose or add therapy if needed. Watch for hypoglycemia if niacin is later stopped.
What other medicines interact with Vitamin b3?
MediHelp also lists interactions of Vitamin b3 with, for example, Lovastatin, Simvastatin, Atorvastatin. The full list is on the Vitamin b3 page.
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