Liraglutide, a glucagon-like peptide (GLP-1) receptor agonist, has showed 
favorable effects in the glycaemic control and weight reduction in patients with 
type 2 diabetes mellitus (T2DM). The meta-analysis was to compare the efficacy 
and safety of liraglutide added to metformin with other treatments in patients 
with T2DM. A systematic literature search on PubMed, Embase, Web of Science and 
the Cochrane library databases were performed. Eligible studies were randomized 
controlled trials (RCTs) of patients with T2DM who received the combination 
treatment of liraglutide and metformin. Pooled estimates were performed using a 
fixed-effects model or random-effects model. A total of nine RCTs met the 
inclusion criteria. Compared with control (placebo, sitagliptin, glimepiride, 
dulaglutide, insulin glargine, and NPH), liraglutide in combination with 
metformin resulted in significant reductions in HbA1c, bodyweight, FPG, and PPG, 
and similar reductions in SBP, and DBP. Moreover, liraglutide combined with 
metformin did not increase the risk of hypoglycemia, but induced a higher 
incidence of gastrointestinal disorders. In conclusion, this meta-analysis 
confirmed the use of liraglutide as add-on to metformin appeared to be effective 
and safe for patients with T2DM. However, considering the potential limitations 
in this study, more large-scale, well-conducted RCTs are needed to identify our 
findings.