ModerateVitamins. Haemopoietic stimulants×Biguanides. Oral antihyperglycemic agents
Updated · Methodology
Mechanism
Metformin suppresses calcium-dependent absorption of the B12-intrinsic factor complex in the terminal ileum. With over 4 years of therapy, clinically significant B12 deficiency is reported in 10–30% of patients.
Symptoms
Fatigue, pallor, paraesthesias in hands and feet, gait instability, memory decline. Develops over 2–4 years of unrecognised therapy.
Management
On long-term metformin, check B12 yearly. If it falls below 200 pg/mL, give cyanocobalamin 500–1000 mcg/day orally or 1000 mcg/week intramuscularly (in significant neuropathy). Supplementation does not cancel the metformin indication.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- PubMed: Metformin use and vitamin B12 deficiency: a systematic review and meta-analysis (2020)
- AEMPS: Ficha técnica: Cianocobalamina (nº registro 85938), sección 4.5 (2021)– AEMPS, CIMA, nº registro 85938, revisión 07/2021, sección 4.5