Why is this important?
Metformin is widely used in type 2 diabetes, including in many patients with heart failure. Observational data have suggested that it may provide cardiovascular benefits beyond glucose lowering, but this has never been clearly established in a large long-term randomised trial.
The Met-HeFT trial, presented at ESC Congress 2026, directly tested whether metformin improves cardiovascular outcomes in patients with HFrEF and diabetes, prediabetes or increased diabetes risk.
What did Met-HeFT ask?
Does metformin reduce major cardiovascular events in patients with HFrEF?
The trial specifically examined whether metformin has an independent cardioprotective effect beyond its established glucose-lowering role.
Who was studied?
Met-HeFT included 940 patients with symptomatic chronic heart failure and LVEF ≤40%. Patients had type 2 diabetes, prediabetes or increased diabetes risk. Only around 10% had established type 2 diabetes, which is important when interpreting the results.
| Key feature | Met-HeFT |
|---|---|
| Participants | 940 |
| Mean age | 70 years |
| Women | 16% |
| Treatment | Metformin vs placebo |
| Mean follow-up | 3.7 years |
Did metformin reduce cardiovascular events?
No significant benefit was demonstrated. The primary endpoint was a composite of death, worsening heart failure, acute myocardial infarction or stroke.
25.1% with metformin vs 23.4% with placebo. HR 1.10; 95% CI 0.84–1.42; P=0.48. Metformin therefore did not significantly improve the primary cardiovascular outcome.
Secondary outcomes, including all-cause death, unplanned heart failure events, new-onset diabetes and change in NT-proBNP, were also not significantly improved.
Does this mean metformin is harmful in HFrEF?
No. Metformin was not associated with significant cardiovascular harm and remains useful for glucose lowering when clinically indicated.
The key message is different: Met-HeFT did not support the idea that metformin provides an additional independent cardioprotective benefit in HFrEF.
Did the wider evidence agree?
Yes. An accompanying meta-analysis included three heart failure trials involving 1,077 patients and four ischaemic heart disease trials involving 1,123 patients.
It similarly found no significant cardiovascular benefit with metformin in HFrEF and no significant effect in established ischaemic heart disease.
What should clinicians remember?
Metformin retains its established metabolic role, but it should not be expected to reduce cardiovascular events in HFrEF through an additional cardioprotective effect based on the current randomised evidence.
Clinical takeaway
Metformin failed to significantly reduce cardiovascular events in Met-HeFT. It remains beneficial for glucose lowering and was not associated with harm, but current randomised evidence does not support an additional independent cardioprotective benefit in HFrEF.
Full reference
European Society of Cardiology. No significant evidence for protection against cardiovascular outcomes with metformin in heart failure. ESC Press Release. 30 August 2026. Met-HeFT trial and accompanying meta-analysis presented at ESC Congress 2026, Munich, Germany.
American College of Cardiology. H-HeFT and Met-HeFT: No Significant Reduction in CV Events Among HF Patients. ACC News Story. 30 August 2026.