ABSTRACT
Objective To systematically evaluate the effects of metformin on serum vitamin B12,folic acid and homocysteine (Hcy) levels in the patients with type 2 diabetes mellitus (T2DM).Methods The databases of Cochrane Library,EMbase,PubMed,CBM,CNKI,VIP and Wanfang were retrieved by computer to collect the randomized controlled trials (RCTs) on the association between metformin and serum vitamin B12 level in T2DM patients.Two researchers independently screened the literatures,assessed the risk of bias of included RCTs and extracted the data.The RevMan5.3 software was used for conducting the meta analysis.Results A total of 5 RCTs were included.The Meta-analysis results showed that serum vitamin B12 level in the metformin group was significantly decreased compared with the placebo group (MD=-55.86,95 ％ CI(-86.89,-24.84),P =0.000 4);the subgroup analysis showed that serum vitamin B12 level was negatively correlated with the duration of diabetes,metformin use time and dose.The serum Hcy level in the metformin group was increased compared with the placebo group (MD=2.44,95 ％ CI(1.41,3.46),P＜0.01);the serum folic acid level had no statistical differences between the two groups [MD=-2.39,95 ％CI (-4.93,0.15),P=0.06];the incidence rate of adverse reactions in the metformin group was higher than that in the placebo group[RR=2.0,95 ％ CI(1.32,3.03),P =0.001].Conclusion Metformin treatment may lead to decrease of serum vitamin B12 level and increase of Hcy level while has no obvious influence on the folic acid level in T2DM patients,but has higher incidence rate of adverse reactions.