Evaluation serum vitamin B12 levels of patients with type 2 DM who are taking metformin

The most frequent side effects of metformin, which is the first choice oral antidiabetic drug in patients with Type 2 Diabetes Mellitus (DM), include gastrointestinal symptoms, such as nausea and bloating. However, malabsorption of vitamin B12 in patients on metformin treatment usually does not considered by physicians. In our study, we aimed to compare the serum vitamin B12 levels among patients with type 2 DM who were on metformin treatment, patients with type 2 DM who were receiving antidiabetic drugs other than metformin and healthy volunteers. For this purpose; 30 patients with type 2 DM treated with metformin, 30 patients with type 2 DM treated with antidiabetics other than metformin and 30 healthy volunteers included to our study. Blood samples of patients were taken at the time of admission and fasting blood glucose (FBG), HbA1c, hemoglobin (HGB), WBC, PLT, creatinine, ALT, serum vitamin B12 levels were measured. Average levels of vitamin B12 was detected 154 pg/ml (63-355) in metformin group, 278 pg/ml (119-753) in other diabetic patients treated with other antidiabetic agents and 271 pg/ml (110-563) in the control group. This difference between the groups was statistically significant (p <0.001). The patients in metformin group further analyzed according to the duration of metformin treatment; the subgroups were either consisted of patients receiving metformin for less than 4 years or for at least 4 years. The significant difference were found between serum vitamin B12 levels of patients who were on metformin for less than 4 years and for at least 4 years (p <0.001). As a result, we showed the correlation between metformin treatment, the duration of metformin treatment and vitamin B12 deficiency. We suggest that serum vitamin B12 levels should be monitored and replaced, if necessary, especially in diabetic patients receiving metformin for 4 or more years. Key words: Type 2 diabetes mellitus, Metformin, Vitamin B12