The Met-HeFT trial reveals that metformin does not significantly lower the risk of major cardiovascular events in patients with heart failure and reduced ejection fraction, challenging previous observational data suggesting potential benefits.
Metformin does not appear to reduce the risk of major cardiovascular events in people with heart failure and reduced ejection fraction, according to the Met-HeFT trial presented at ESC Congress 2026 and reported by MedicalXpress. The study adds rare randomised evidence to a question that has long been shaped more by observational data than by large controlled trials.
In the investigator-led, double-blind trial, 940 patients in Denmark with symptomatic chronic heart failure and an ejection fraction of up to 40% were assigned to metformin or placebo. Participants were an average of 70 years old, and only 16% were women. Over a mean follow-up of 3.7 years, metformin made no meaningful difference to the combined outcome of death, worsening heart failure, heart attack or stroke, nor to secondary measures including all-cause mortality and heart-failure admissions, according to the reports from the American College of Cardiology and other congress coverage.
The findings also align with a separate meta-analysis presented at the same meeting by Anders Hostrup Larsen of Goedstrup Hospital in Herning, Denmark. That review pooled three heart-failure trials involving 1,077 patients and four studies in ischaemic heart disease involving 1,123 patients, and likewise found no significant cardiovascular benefit from metformin in patients with reduced ejection fraction or established ischaemic heart disease.
The results may not close the book on metformin in heart failure, but they do narrow its appeal as a drug with hoped-for heart protection beyond glucose control. Henrik Wiggers, the trial’s principal investigator at Aarhus University Hospital, said the treatment was not linked to harm and remains useful for lowering blood sugar, but the new evidence does not support claims of an independent cardioprotective effect. He also noted a limitation of the trial: only about one in 10 participants had type 2 diabetes, reflecting how widely metformin is already used and the difficulty of stopping it for study entry.
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