What happened
Metformin shows no benefit over placebo for major cardiovascular events in chronic heart failure.
Multiple experts agree the result is clearly neutral, with metformin showing no cardiovascular benefit beyond its metabolic effects in HFrEF patients with diabetes or prediabetes.
Experts uniformly read Met-HeFT as a clearly neutral trial, confirming that metformin does not provide cardiovascular benefit beyond glucose lowering in heart failure with reduced ejection fraction.
The cardiology community views this as a definitive negative result that closes a longstanding question about whether metformin has independent cardioprotective effects in heart failure. No expert disputes the neutral finding, and the trial's principal investigators emphasize that a companion meta-analysis in ischaemic heart disease was also negative. The remaining question is whether this reshapes guideline language around metformin's role in heart failure patients with diabetes.
Whether guidelines will now explicitly state that metformin should not be expected to confer cardioprotection in heart failure remains an open question.
Martha Gulati flagged the trial's heavily male enrollment, raising the question of whether results can be generalized to women.
“Metformin was not associated with any harm and it still remains beneficial in terms of glucose lowering, but our analyses indicate no significant evidence for any independent cardioprotective benefits.”
Conference Coverage ↗From published coverage, not an answer posted here.
Martha Gulati
Endpoint critiqueCardiologistNeutral result, but the mostly male enrollment limits generalizability
X post ↗
Evidence-based medicine finally catches up with metformin's assumed CV benefits
X post ↗
Primary outcome clearly neutral with a hazard ratio crossing unity
X post ↗Anders Hostrup Larsen
Results readoutAssociate professor, Goedstrup Hospital, DenmarkNo effect in heart failure or established ischaemic heart disease
Original post ↗
The largest randomized trial confirms metformin does not protect the heart in HFrEF
X post ↗
Metformin did not reduce the composite primary endpoint in HFrEF
X post ↗
Flags Met-HeFT alongside H-HeFT as new heart failure evidence from the Hot Line 6 session.
X post ↗Upvote a question you would like answered, or open it to join the discussion.
Why the trial, key points, tables, limitations, PICO, abstract, media & sources
Why the trial?
Metformin is first-line in type 2 diabetes and observational data hint at benefit in heart failure, but it had never been tested in a randomised cardiovascular outcomes trial in patients with reduced ejection fraction.
Does metformin reduce the composite of death, worsening heart failure, acute myocardial infarction, or stroke in patients with symptomatic chronic heart failure (LVEF ≤40%) and diabetes or prediabetes?
| Outcome | Metformin | Placebo |
|---|---|---|
| Death, worsening HF, acute MI, or stroke | 25.1% | 23.4% |
| HR 1.10 (95% CI 0.84-1.42; p=0.48) · not significant | ||
Safety
metformin was not associated with harm per the record; no event counts reported.
Statistical certainty
sample size and per-arm counts are not reported in the record (press-release source), and the confidence interval (0.84-1.42) is wide enough to include meaningful benefit or harm.
Design limitations
secondary endpoints (all-cause death, unplanned HF events, new-onset diabetes, NT-proBNP) are reported as null results without numbers.
Does metformin reduce the composite of death, worsening heart failure, acute myocardial infarction, or stroke in patients with symptomatic chronic heart failure (LVEF ≤40%) and diabetes or prediabetes?
In patients with HFrEF and dysglycemia, metformin did not reduce the risk of a composite cardiovascular and heart failure endpoint compared to placebo over a 3.7-year follow-up.
No takes yet. Share an insight, caveat, or question.
Expert reaction
ESC Congress 2026
Expert labels are toward Met-HeFT's result, from named public quotes (n=2). As of Aug 31, 2026.
Experts uniformly read Met-HeFT as a clearly neutral trial, confirming that metformin does not provide cardiovascular benefit beyond glucose lowering in heart failure with reduced ejection fraction.
The cardiology community views this as a definitive negative result that closes a longstanding question about whether metformin has independent cardioprotective effects in heart failure. No expert disputes the neutral finding, and the trial's principal investigators emphasize that a companion meta-analysis in ischaemic heart disease was also negative. The remaining question is whether this reshapes guideline language around metformin's role in heart failure patients with diabetes.
Multiple experts agree the result is clearly neutral, with metformin showing no cardiovascular benefit beyond its metabolic effects in HFrEF patients with diabetes or prediabetes.
What they’re arguing about
supportiveneutralcautiouscritical
Counts are expert takes we classified by axis. Tap a row to see the takes behind its count.
Whether guidelines will now explicitly state that metformin should not be expected to confer cardioprotection in heart failure remains an open question. Martha Gulati flagged the trial's heavily male enrollment, raising the question of whether results can be generalized to women.
Gulati highlights the clearly negative primary endpoint but flags that the trial enrolled mostly men, questioning how broadly the findings can be applied.
Santas frames Met-HeFT as overdue confirmation that the cardiovascular halo around metformin is not supported by rigorous trial data in heart failure on top of contemporary guideline-directed therapy.
As lead investigator, Wiggers notes metformin remains useful for glucose lowering but the analyses show no significant evidence for any independent cardioprotective benefit.
Metformin conferred no event reduction in this RCT of chronic HF; challenges observational signals of benefit and does not support its use to improve cardiovascular outcomes.
Met-HeFT was an investigator-initiated, double-blind trial at 23 centres in Denmark, run as part of DANHEART's factorial design alongside H-HeFT. Participants had symptomatic chronic heart failure, a left ventricular ejection fraction of up to 40%, and type 2 diabetes, prediabetes, or increased risk of type 2 diabetes, and were randomised to metformin or placebo. Over a mean follow-up of 3.7 years there was no significant difference between metformin and placebo for the primary endpoint of death, worsening heart failure, acute myocardial infarction or stroke (25.1% vs 23.4%; HR 1.10, 95% CI 0.84 to 1.42; p=0.48). Metformin did not significantly affect secondary endpoints including all-cause death, unplanned heart-failure events, new-onset diabetes, or change in NT-proBNP, and was not associated with harm. Source: ESC Congress 2026 press release, 30 August 2026.
Journal, society, and media accounts. Useful signal, not independent expert judgment.
Henrik Wiggers (2026) conducted an RCT in chronic heart failure. Metformin vs. placebo was evaluated on death, worsening heart failure, acute myocardial infarction or stroke (HR 1.10, 95% CI 0.84 to 1.42, p=0.48). Metformin did not significantly reduce death, worsening heart failure, MI, or stroke compared to placebo (25.1% vs 23.4%; HR 1.10, 95% CI 0.84-1.42, p=0.48).
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