Therapeutic Research

Abstract

It has been recently reported that metformin result in reducing the serum vitamin B12（Vit B12）level in patients with diabetes, and American Diabetes Association （ADA） recommended the regular measurement of Vit B12 in 2017. However, since we could not actually feel the decrease, we examined the effect of metformin on the changes of Vit B12, folic acid and red blood cells in patients with diabetes in the study. 304 patients with diabetes undergoing outpatient treatment in our hospital, were divided metformin‒treated（n＝212）and control（n ＝92）groups, and the clinical parameters, including age, gender, duration of diabetes, body mass index, blood pressures, plasma levels of glucose, HbA1c （NGSP value）, serum levels of Vit B12 and folic acid, blood cell counts, and presence of atrophic gastritis and peripheral neuropathy, were compared. In addition, the current dosage, the administration period, and the total administered amount of metformin were evaluated in the metformin‒treated group. There were not different in the levels of Vit B12, folic acid and red blood cell volume（MCV） between two groups. On the current dosage of metformin, the Vit B12 level in the metformin‒treated group was significantly lower than that of the control group, and the level was dose‒dependently decreased within the reference range. In contrast, the levels of folic acid and MCV were not changed by metformin. In addition, although there was no difference in the administration period of metformin, the level of Vit B12 at 3000 g or more was significantly lowered than that at 1000 g or less within the reference range. This study suggested that the reduction of Vit B12 by the treatment with metformin might not be observed in Japanese patients with diabetes, unlikely to ADA recommendation.