Effect of metformin on serum vitamin B12 and red blood cell indices in North Indian subjects with diabetes mellitus

Abstract

Background: Diabetes mellitus (DM) affecting almost half a billion people worldwide and India is amongst the top ten countries of adults with diabetes. Metformin, the first-line therapy for diabetes, is associated with vitamin B12 malabsorption and subsequently, the development of vitamin B12 deficiency/insufficiency could manifest severe complications like neuropathy or anemia in the future. This study evaluated the effect of metformin on vitamin B12 and RBC indices in the North Indian population.Methods:This study was executed at a tertiary care hospital. 35 T2DM (type 2 DM) participants with ongoing metformin therapy were compared with 27 T2DM participants without metformin therapy. Participants were recruited from outpatient after diagnosis as per American diabetes association (ADA) criteria.Results: Metformin-treated participants had significantly low hemoglobin (t=2.096, df=60, 0.0403) compared to untreated participants. Similarly, MCHC was significantly lower in the metformin group (mean=33.28 gm/dl) compared to non-metformin group (mean=34.53 gm/dl) (t=2.745, df=60, p=0.0080). Moreover, there was a strong negative correlation (r=-0.4613, p=0.0053) among vitamin B12 and MCV in metformin group. There was no statistically significant correlation between vitamin B12 and RBC indices (MCV, MCH, MCHC) in the non-metformin group. Analyzing contingency table (Fisher’s exact test), we found no major difference (p=0.2002) between two groups of vitamin B12 with an odds ratio of 2.026 (95% CI=0.7366 to 5.633). Unpaired t test also confirmed insignificancy (t=0.04077, df=60, p=0.9676).Conclusions:Strong negative correlation was observed between vitamin B12 and MCV. Despite the insignificant difference of vitamin B12 between metformin and non-metformin groups, significantly low MCHC was found in metformin-treated participants.