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An Updated Systematic Review and Meta-Analysis on the Efficacy and Safety of Metformin as Add-on Therapy to Insulin in Patients With Type 1 Diabetes

Masouri MM, Ebrahimi R, Noori S

Endocrinology, diabetes & metabolism, 2025

2,051 participants · 5 citations

Abstract

INTRODUCTION: This study aims to perform an updated meta-analysis evaluating the efficacy and safety of metformin adjunct therapy in type 1 diabetes mellitus (T1DM) patients.

METHOD: Cochrane, PubMed and Embase were searched for randomised controlled trials (RCTs) that reported the efficacy and safety of metformin in T1DM patients. Statistical analyses were performed using STATA software.

RESULTS: Twenty-nine placebo-controlled RCTs enrolling 2051 T1DM patients were included. Adolescents experienced a notable reduction in total insulin daily dose (TIDD) (mean difference [MD] = -0.61 [95% confidence interval (CI): -1.02, -0.20] units/kg per day) and levels of haemoglobin A1c (HbA1c) (MD = -0.45 [95% CI: -0.79, -0.11]), total cholesterol (TC) (MD = -0.78 [95% CI: -1.54, -0.02]), and low-density lipoprotein (LDL) (MD = -0.69 [95% CI: -1.36, -0.02]) at 3 months of follow-up with metformin. In adults, metformin significantly reduced Body Mass Index (BMI) (MD = -0.71 [95% CI: -1.23, -0.19]), TIDD (MD = -0.44 [95% CI: -0.73, -0.16]), and levels of HbA1c (MD = -0.70 [95% CI: -1.10, -0.30]) and TC (MD = -0.60 [95% CI: -1.09, -0.10]) at 6 months. The risk of gastrointestinal adverse events (GIAEs) was significantly higher in both adolescents (Relative Risk [RR] = 1.74 [95% CI: 1.38, 2.21]) and adults (RR = 3.24 [95% CI: 1.49, 7.02]). All of the above had p-values less than 0.05. The metformin group showed no differences in BMI Z-score, high-density lipoprotein (HDL) level, or diabetic…

How strong is the evidence?

Evidence Hub reads this as a meta-analysis, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 2,051 participants or records.

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