Objective To evaluate the efficacy and safety of metformin in patients with lung cancer with type 2 diabe-tes.Methods The clinical data of 60 patients with stage 2 lung cancer complicated with type 2 diabetes admitted to Fujian Cancer Hospital from January 2022 to October 2023 were retrospectively selected.According to different hypo-glycemic treatment schemes,they were divided into observation group and control group,with 30 cases in each group.The observation group was given metformin tablets combined with chemotherapy,and the control group was given acar-bose tablets combined with chemotherapy.The clinical efficacy,blood glucose level and incidence of adverse reac-tions were compared between the two groups.Results The total effective rate of diabetes treatment in the observation group was higher than that in the control group,the difference was statistically significant(P<0.05).After treatment,the levels of fasting plasma glucose,2-hour postprandial plasma glucose and glycated hemoglobin A1c in the obser-vation group were lower than those in the control group,and the differences were statistically significant(all P<0.05).There was no significant difference in the incidence of adverse reactions between the two groups(P>0.05).Conclusion The total effective rate of metformin in the treatment of patients with stage 2 lung cancer complicated with type 2 diabetes was higher,the decline of blood glucose was more obvious,and the incidence of adverse reactions did not change significantly.