Background: several studies have found association between metformin and B12 deficiency (BMJ 2010; 340:2181).
Diabetes Prevention Program, n = 3200 randomized to placebo, metformin or intensive lifestyle tx.
After trial ended in 2002, metformin group (n = 1700) offered continued metformin.
Of pts on metformin, 4% had B12 deficiency compared to 2% of non-metformin group.
Also had higher homocysteine levels, as expected.
Difference decreased but continued out to 13 years of follow-up.
Conclusion: clinical significance is unclear; no data on higher MCVs or neuropathy rates; should not screen B12 in metformin pts yet.
J Clin Endocrinol Metab 2016 Apr; 101: 1754