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Published on: 7/21/2026

Can metformin cause vitamin deficiency?

Yoshinori Abe

Reviewed by Yoshinori Abe, MD

Internal Medicine

Metformin and Vitamin B12 Deficiency: What to Know

Metformin, a widely prescribed medication for type 2 diabetes, can cause vitamin B12 deficiency, particularly with long-term or high-dose use. Studies suggest that up to 30% of people taking metformin may develop lower B12 levels over time. This happens because metformin can interfere with the absorption of B12 in the small intestine.

Symptoms of B12 deficiency include fatigue, weakness, numbness or tingling in the hands and feet, memory issues, and mood changes. Left unaddressed, it may lead to nerve damage or anemia. Regular B12 monitoring and supplementation may help those on metformin maintain healthy levels.

If you're taking metformin and noticing unusual symptoms, don't guess—get clarity. Understanding whether your symptoms point to a B12 deficiency or something else is the first step toward feeling better. Take a free, instant, online symptom check to explore what may be behind your symptoms and confidently plan your next steps.

Reviewed for medical accuracy: 07/20/2026

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Important Next Steps

Learn if metformin causes vitamin deficiencyDiscover likely vitamin deficiencies from metforminFind out if metformin affects energySee OTC options for deficiency symptomsFind a doctor for metformin concernsUnderstand home remedies for deficiency symptomsCheck if your symptoms need care

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Explanation

Metformin is a medication often used to help control blood sugar levels in people with diabetes. However, using it for a long time can sometimes cause a decrease in vitamin B12 levels in the body.

How Does This Happen?

  • Vitamin B12 Absorption: Metformin can affect how the body absorbs vitamin B12 from food. Over time, this may lead to lower levels of this important vitamin.

Why Is Vitamin B12 Important?

  • Nerve Health: Vitamin B12 is crucial for keeping nerves healthy.
  • Blood Health: It also helps in making healthy blood cells.

What Can Be Done?

  • Monitoring: People taking metformin, especially for a long time, should have their vitamin B12 levels checked regularly.
  • Supplements: If levels are low, doctors might suggest vitamin B12 supplements.

If you're experiencing unusual symptoms while taking metformin, consider using a free symptom checker to help understand what might be causing them and whether you should discuss vitamin B12 testing with your doctor.

(References)

  • Bell DSH. (2022). Metformin-induced vitamin B12 deficiency can cause or .... Diabetes, obesity & metabolism, 35491956.

  • Infante M, Leoni M, Caprio M, & Fabbri A. (2021). Long-term metformin therapy and vitamin B12 deficiency. World journal of diabetes, 34326945.

  • Niafar M, Hai F, Porhomayon J, & Nader ND. (2015). The role of metformin on vitamin B12 deficiency: a meta- .... Internal and emergency medicine, 25502588.

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