Metformin and Vitamin B12 Deficiency: A Prevalence Study
Authors' conclusion
Vitamin B12 deficiency was uncommon with no meaningful excess risk among metformin users.
Study context
- Population
- Adults with diabetes (type 1, 2, other types) attending 2 outpatient clinics in Denmark, March 2024 to October 2025; median age 54 years, 57% male
- Participants
- 3,958 adults
- Exposure
- Current metformin use vs non-use
- Outcome
- Prevalence of vitamin B12 deficiency (plasma B12 ≤ 250 pmol/L and elevated serum methylmalonic acid)
Methodological details2 outpatient clinics, Prevalence differences and ratios estimated by binomial regression
- 2 outpatient clinics
- Prevalence differences and ratios estimated by binomial regression
Main finding
As reported in the abstract
Vitamin B12 deficiency prevalence
Each group vs non-usersAdjusted prevalence ratio (95% CI)
Current users
1.56(0.92–2.63)
- Current users
- aPD 0.7% (95% CI −0.32 to 1.7)
Observational data: associations, not effects.
Further findings
Vitamin B12 deficiency prevalence, T2D subgroup (n = 1,338, median age 62 years, 61% male)
- Prevalence, metformin current users vs non-users
- 2.3% versus 2.0%
- aPD
- 0.38% (95% CI −1.9 to 1.1)
- aPR
- 1.21 (95% CI 0.55 to 2.66)
Original publication
Metformin and Vitamin B12 Deficiency: A Prevalence Study. Endocr Pract. Published 7 August 2026. doi:10.
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