Folic acid × Metformin

Metformin on long-term use (over 5 years) moderately reduces blood B12 (by 10–30%). Effect on folate is minimal. Folate deficiency on metformin has not been described.

The combination usually causes no specific symptoms. Each drug's individual side effects remain.

No folate dose adjustment needed. On long-term metformin, check B12 yearly. For pregnancy planning in women with diabetes, folic acid 400–800 mcg/day is standard regardless of metformin.