Met-HeFTHeart FailureOpen Access
Effects of Metformin in Patients With Chronic Heart Failure and Dysglycemia
Metformin in patients with chronic heart failure
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.
Population
Patients with symptomatic HFrEF (LVEF <=40%) + dysglycaemia; N not reported
Comparison
Metformin vs placebo
Design
Investigator-initiated double-blind RCT, 23 Danish centres (DANHEART factorial)
Follow-up
Mean 3.7 years
Key result
Metformin did not significantly reduce the risk of death, worsening heart failure, acute myocardial infarction, or stroke compared to placebo (HR 1.10; 95% CI 0.84-1.42; p=0.48).
Authors
Discussion
Key questions
Member takes
Where experts stand
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.
Agreement
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.
4 clinicians say this directly
What they’re arguing about
supportiveneutralcautiouscritical
Counts are expert takes we classified by axis. Tap a row to see the takes behind its count.
Still unclear
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.
Key expert perspectives
MGMartha GulatiCardiologistEndpoint critiqueAug 31
Neutral result, but the mostly male enrollment limits generalizability
Gulati highlights the clearly negative primary endpoint but flags that the trial enrolled mostly men, questioning how broadly the findings can be applied.
Distilled from their postX post
Evidence-based medicine finally catches up with metformin's assumed CV benefits
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.
Distilled from their postX post
HWHenrik WiggersCardiologist, Aarhus University Hospital, DenmarkResults readoutAug 30
No harm from metformin, but no independent cardioprotective benefit either
As lead investigator, Wiggers notes metformin remains useful for glucose lowering but the analyses show no significant evidence for any independent cardioprotective benefit.
Distilled from their postOriginal post
Overview
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.
Key Points
- To evaluate the efficacy and safety of metformin in reducing major cardiovascular outcomes in patients with symptomatic chronic heart failure and dysglycemia.
- Double-blind, randomized controlled trial conducted across 23 centres in Denmark with a mean follow-up of 3.7 years.
- Enrolled participants with symptomatic chronic heart failure, left ventricular ejection fraction up to 40%, and type 2 diabetes, prediabetes, or high risk of type 2 diabetes, randomized to metformin or placebo.
- The primary composite endpoint of death, worsening heart failure, acute myocardial infarction, or stroke occurred in 25.1% of the metformin group versus 23.4% of the placebo group (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.
Evidence details
What drove the result?
| 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 | ||
Limitations & tradeoffs
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.
PICO
P
Population
Patients with symptomatic chronic heart failure (LVEF ≤40%) and type 2 diabetes, prediabetes, or increased risk of type 2 diabetes, followed for a mean of 3.7 years.
I
Intervention / Comparator
Metformin vs Placebo
O
Primary Outcome
Death, worsening heart failure, acute myocardial infarction or stroke — HR 1.10 (0.84 to 1.42), p=0.48
Main Result
Hazard Ratio: 1.1 (95% CI 0.84–1.42)
Absolute Event Rate: 25.1% vs 23.4%
p-value: p=0.48
Coverage & sources
Journal, society, and media accounts. Useful signal, not independent expert judgment.
Cite This Study
Henrik Wiggers (2026) conducted an RCT in Symptomatic 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 the risk of death, worsening heart failure, acute myocardial infarction, or stroke compared to placebo (HR 1.10; 95% CI 0.84-1.42; p=0.48).