Inpatient Metformin Utilization and Post-hospitalization Clinical Outcomes: An Observational Cohort Study.

Gallo RJ, Lin S, Fang DZ, Glassman PA, Sahay A, Heidenreich PA. Inpatient Metformin Utilization and Post-hospitalization Clinical Outcomes: An Observational Cohort Study. Journal of general internal medicine. 2025 Feb 3 DOI: 10.1007/s11606-025-09384-y.

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Abstract:

BACKGROUND: Metformin is the first-line treatment for diabetes, with multiple long-term benefits. However, there is limited evidence for its use in the inpatient setting, and clinical guidelines have historically recommended holding oral diabetes medications during acute hospitalization. While studies have not found evidence of harm from continuing metformin during hospitalization, withholding may lead to unnecessary insulin prescriptions, which in turn may lead to hypoglycemia events after discharge and other associated complications. OBJECTIVE: To investigate the association between metformin use during hospitalization and post-hospitalization outcomes. DESIGN: Observational cohort study from January 2016 to January 2022, emulating a target trial. PARTICIPANTS: Adults with type 2 diabetes admitted to a Veterans Health Administration hospital for common medical conditions. INTERVENTIONS: Continuation of an outpatient metformin prescription during hospitalization. MAIN MEASURES: Hypoglycemia within 90 days of discharge. Secondary outcomes included insulin prescriptions at discharge, 90-day readmissions, and 90-day mortality. KEY RESULTS: The propensity-matched cohort included 67,162 hospitalizations, equally split between those who did and did not have metformin continued during hospitalization. Within 90 days of hospital discharge, those that received metformin had lower risk of hypoglycemia (1.5% vs 1.8%; OR 0.83, 95% CI 0.73-0.93; p = 0.003), readmissions (29.4% vs 30.6%; OR 0.96, 95% CI 0.92-1.00; p = 0.03), and mortality (6.4% vs 7.4%; OR 0.86, 95% CI 0.80-0.92; p < 0.001). Patients receiving metformin also had lower risk of insulin prescriptions at discharge (18.5% vs 20.3%; OR 0.89, 95% CI 0.84-0.95; p < 0.001). CONCLUSIONS: Continuation of metformin during hospitalization for patients with type 2 diabetes was associated with decreased risk of post-hospitalization insulin prescriptions and 90-day hypoglycemia, readmissions, and mortality. These findings question clinical guideline recommendations to hold metformin during hospitalization.