We read with great interest the case report by Gilligan1 about metformin-associated vitamin B12 deficiency. To date, only case reports or small studies have described patients with biguanide-associated decreased vitamin B12 levels or true vitamin B12 deficiency. Thus, we would like to offer some elements about our own experience with this unfamiliar cause of cobalamin deficiency in adults.
Andrès E, Noel E, Goichot B. Metformin-Associated Vitamin B12 Deficiency. Arch Intern Med. 2002;162(19):2251–2252. doi: