Analysis of 48,214 FDA adverse event reports found GLP-1 receptor agonist/metformin combination therapy had lower adverse event rates than monotherapy, with unexpected signals for kidney injury and pancreatic cancer and notable gender differences in side effect timing.
48,214 adverse event reports analyzedThis 20-year analysis of the FDA's adverse event database is one of the largest pharmacovigilance studies specifically examining the GLP-1 RA/metformin combination, revealing unexpected safety signals and gender-specific risk patterns.
What the researchers found
Analysis of 48,214 FAERS reports (57.5% female) found that GLP-1 receptor agonist plus metformin combination therapy had lower adverse event rates than either drug alone (monotherapy). Common AEs were nausea and weight loss. Unexpected safety signals included kidney injury and pancreatic cancer. Gender-specific patterns emerged: males reported more renal calculi and early-onset AEs (within 30 days), while females experienced more delayed AEs (beyond 360 days). Weight loss was consistent across all demographic groups.
Why it matters
GLP-1 RAs combined with metformin is one of the most common diabetes drug combinations prescribed worldwide. This large pharmacovigilance analysis of 20 years of adverse event data provides clinicians with actionable safety insights, including the surprising finding that combination therapy appears safer than monotherapy and the identification of gender-specific risk patterns that could inform personalized monitoring strategies.
How the study worked
Retrospective disproportionality analysis of the FDA Adverse Event Reporting System (FAERS) database from 2004 to 2024. The reporting odds ratio (ROR) was used as the primary measure, with Bayesian confidence propagation neural network (BCPNN) for sensitivity analysis. Adverse events were compared between GLP-1 RA/metformin combination therapy and monotherapy with either drug alone. Stratified analyses were performed by gender, age, and body weight.
Who was studied
48,214 adverse event reports from the FAERS database (2004-2024) involving GLP-1 receptor agonists and/or metformin, 57.5% female
What this study cannot tell us
FAERS is a voluntary adverse event reporting system subject to reporting bias, underreporting, and confounding by indication. The finding that combination therapy had lower AE rates than monotherapy may reflect healthier-user bias or differences in prescribing patterns rather than true superior safety. Disproportionality analysis can identify safety signals but cannot establish causation. The unexpected signals for kidney injury and pancreatic cancer require prospective confirmation.
How to read the evidence
This is a retrospective pharmacovigilance analysis using the FAERS database with disproportionality analysis and Bayesian sensitivity checks. While the large dataset and long timeframe are strengths, FAERS data is subject to reporting bias, cannot establish causation, and lacks denominator data (total number of prescriptions). Safety signals require prospective confirmation.
When this study was published
Published in 2025 with data through 2024, this is a very current safety analysis covering the full modern era of GLP-1 receptor agonist use alongside metformin.
The bigger picture
As GLP-1 receptor agonists are increasingly prescribed for both diabetes and obesity, understanding their real-world safety profile in combination with metformin — the most commonly co-prescribed drug — is essential for clinical practice. This study is part of a growing body of pharmacovigilance research using large-scale databases to identify safety patterns that may not emerge from controlled clinical trials, which typically exclude the complex, multi-morbid patients who make up the real-world user base.
Questions still open
- Are the kidney injury and pancreatic cancer signals true drug effects, or artifacts of reporting bias and confounding by indication?
- Why do men and women show different timing patterns for adverse events with this combination therapy?
- Should monitoring protocols for GLP-1 RA/metformin combination therapy be differentiated by gender based on these findings?
Common questions
Does this study prove that taking GLP-1 drugs with metformin is safer than taking either drug alone?
Should I be worried about kidney injury or pancreatic cancer from this drug combination?
Read the original research
Disproportionality analysis of GLP-1 receptor agonists combined with metformin based on the FAERS database.
Scientific reports, 15(1), 34673
Citation
Liu, Boyi; Huang, Ruizhe; Zhang, Wenchao; Tian, Jie; Yao, Xian; Chen, Danna. (2025). Disproportionality analysis of GLP-1 receptor agonists combined with metformin based on the FAERS database.. Scientific reports, 15(1), 34673. https://doi.org/10.1038/s41598-025-02394-0