Metformin and vitamin B12: why your doctor checks it
Written by Dr. Vishnu Anjan Nareddy, MD (General Medicine)Professor of Medicine-Senior consultant physician (MD, General Medicine) · 4 min readMetformin, a common diabetes tablet, can lower vitamin B12 levels when taken for a long time. A simple blood test, usually once a year, finds a low level early.
Why does this happen?
Metformin can reduce how much B12 the gut absorbs. The drop is slow and often shows no signs for years.
What signs can low B12 cause?
- Tingling, burning or numbness in the feet or hands
- Tiredness and breathlessness from anaemia
- Poor memory or low mood
Tingling feet can also come from diabetes itself, which is why a test is better than guessing.
Who should get tested?
Anyone who has taken metformin for several years, or who has tingling feet, tiredness or anaemia.
What if my B12 is low?
Your doctor may give B12 tablets or injections. Don't stop metformin on your own; it remains an important diabetes medicine.
From our research
Dr. Vishnu Anjan Nareddy has authored clinical research investigating vitamin B12 levels in patients with type 2 diabetes on long-term metformin therapy, demonstrating the importance of periodic serum B12 assays to prevent diabetic peripheral neuropathy misdiagnosis.
If you take metformin and have not had a B12 test in the last year, or you have new tingling or numbness in your feet.
Book with Dr. VishnuThis guide is general information and not a diagnosis. Reviewed by Dr. Vishnu Anjan Nareddy · October 2026 · How we write and review guides