Effect of Metformin Therapy on Vitamin D and Vitamin B12 Levels in Patients with Type 2 Diabetes Mellitus

A comparative study of levels of vitamin B12 in patients of type 2 diabetes mellitus on metformin and not on metformin at tertiary care center

“…4,[15][16][17][18][19] Metformin use has been unequivocally demonstrated as the prime factor associated with vitamin B12 deficiency among patients with T2DM. [20][21][22][23][24] It was observed that prevalence of decreased serum vitamin B12 status in metformin treated patients in our study was lower than those in the Green et al study. 24 This comparison must be interpreted with caution as there are other factors that may affect the serum Vitamin B12 of these patients which were not addressed in this study (diet, drug interactions etc.).…”

Association between metformin and vitamin B12 deficiency in patients with type 2 diabetes: A systematic review and meta-analysis

“…The 17 cross-sectional studies ( Table 1) indicated either an association of metformin use with a lower B12 concentration (10 studies [17][18][19][20][21][22][23][24][25][26]) or showed no association (7 studies [27][28][29][30][31][32][33]). In terms of cohort-based or retrospective case control studies, 4 studies were included in the review (Table 2) showing a reduction in HoloTC and total vitamin B12 [17] or increased odds of B12 deficiency after 3 years (adjusted OR=2.39 (95% CI 1.46 to 3.91) [34] in metformin users, compared with non-users.…”

Screening the Effect of Metformin on Serum Vitamin B12 and Blood Homocysteine Levels in Patients with Type 2 Diabetes Mellitus

“…Several hypotheses are available; include bacterial overgrowth in the small intestine, changes in small bowel motility, changes in bacterial flora, competitive inhibition or inactivation of vitamin B 12 absorption or an effect of calcium on cell membranes [15,21,23].…”