People with heart failure are often advised to limit their fluid intake. However, a large study led by Radboud University Medical Center now shows that this practice does not provide any health benefits. Researchers writing in Nature Medicine found that it is safe when patients with heart failure regulate their own fluid intake.

This is the first large-scale study examining the effects of fluid restriction in heart failure. The findings show that limiting fluid intake does not improve health outcomes. Whether or not patients followed a restricted fluid intake, there were no differences in health status, hospital admissions, mortality, or medication use. The only noticeable difference was that those with restricted fluid intake experienced more thirst. Apparently drinking less is unnecessary for stable heart failure patients.

Never proven

Patients with heart failure are often advised to drink no more than 1.5 liters of fluid per day. However, the benefits of this intervention have never been scientifically proven. "The idea is that drinking less would help retain less fluid," says cardiologist Roland van Kimmenade from Radboudumc. "But when you think about it, this isn't as logical as it initially seems. The fluid doesn't accumulate in the areas that cause problems in heart failure."

Moreover, fluid restriction has several downsides. Van Kimmenade explains, "It's unpleasant and frustrating. Patients experience stress from thirst and constantly monitoring their intake. It constantly reminds them of their heart failure. Socially, it can also be challenging: if I have a cup of tea now, can I still have coffee with my neighbor?"

Heart pumping strength

In western countries, including the Netherlands, one in five people will develop heart failure during their lifetime, primarily affecting those over sixty. Heart failure occurs due to either reduced pumping strength of the heart or a stiffening of the heart chamber. In both cases, the heart struggles to circulate blood efficiently, leading to fluid buildup in the lungs. 

The study was conducted across seven hospitals and included 506 patients. Half were advised to limit their fluid intake to a maximum of 1.5 liters per day, while the other half could drink as much as they wanted. Over three months, researchers assessed both men and women with different causes of heart failure. Only stable patients were included, excluding those with recent hospital admissions or low sodium levels. The study measured health status, quality of life, thirst, and safety.

Two cups of coffee

Patients who followed the fluid restriction guideline drank no more than 1.5 liters per day. Those without restrictions consumed about 300 milliliters more daily—roughly the equivalent of two cups of coffee. "This might not seem like much, but it appears to be the difference between experiencing thirst or not," says researcher Job Herrmann. "And it aligns with what people over sixty typically drink per day, as they naturally drink less than younger individuals."

Aside from increased thirst in the restricted group, there were no other differences between the two groups. Van Kimmenade concludes, "Our findings show that fluid restriction is unnecessary for stable heart failure patients. This is important for patients worldwide and can be applied immediately. Based on this study, global guidelines can now be updated."

More information: Job J. Herrmann et al, Liberal fluid intake versus fluid restriction in chronic heart failure: a randomized clinical trial, Nature Medicine (2025). DOI: 10.1038/s41591-025-03628-4