02/02/2026
Chronic metformin treatment is associated with Vitamin B₁₂ (cobalamin) deficiency.
Why?
Metformin reduces the absorption of vitamin B₁₂ in the intestine, especially with long-term use.
Possible effects of B₁₂ deficiency:
• Anemia (megaloblastic anemia)
• Peripheral neuropathy (numbness, tingling in hands/feet)
• Fatigue and weakness
Chronic use of metformin, a commonly prescribed medication for type 2 diabetes, has been associated with Vitamin B₁₂ (cobalamin) deficiency. This deficiency occurs due to several factors, including:
1. Malabsorption: Metformin may affect the intestinal absorption of Vitamin B₁₂ by altering the gut microbiome and affecting small intestine motility.
2. Inhibition of Vitamin B₁₂ Transfer: The medication can inhibit the activity of certain factors that are responsible for transporting Vitamin B₁₂ across the intestinal wall into the bloodstream.
3. Increased Gut Bacteria: The alteration in the gut flora can lead to bacterial overgrowth, which can consume Vitamin B₁₂ before it is absorbed.
Treatment Options for Vitamin B₁₂ Deficiency
1. Vitamin B₁₂ Supplements: Oral or intramuscular injections can effectively replenish Vitamin B₁₂ levels in those with a deficiency.
2. Dietary Sources: Increasing intake of Vitamin B₁₂-rich foods can help manage and prevent deficiency:
- Animal Products: Meat, fish, eggs, and dairy products are the primary sources of Vitamin B₁₂.
- Fortified Foods: Some plant-based milk, breakfast cereals, and nutritional yeasts are fortified with Vitamin B₁₂ for those on vegetarian or vegan diets.
3. Monitoring Levels: Regular monitoring of Vitamin B₁₂ levels in patients on long-term metformin therapy is recommended to proactively address any deficiencies.
Conclusion
Patients on chronic metformin therapy should be aware of the potential risk of Vitamin B₁₂ deficiency and discuss with their healthcare provider about monitoring and supplementation options.
