Heart failure is the most common cause of admission to hospital and is associated with high morbidity and mortality. Treatment options consist of medical- and device treatment and self-care strategies, where fluid restriction has been one of the components in the self-care management of patients with chronic heart failure. The medical treatment has progressed and improved over the years and considerably over the last few years, which has decreased symptoms and improved physical function of these patients. Despite our great success in the medical treatment of heart failure, we still face challenges in hospital readmissions and treatment strategies. It contributes to the increased need of evidence on, if and how, fluid intake and fluid restriction should be used as a self-care method. Fluid restriction as a self-care treatment is still commonly recommended in heart failure management although the scientific clinical evidence is lacking. Fluid restriction is associated with a higher degree of thirst and lower rated quality of life, and there is no consensus on how fluid restriction should be used, no plan for individualized treatment and no agreement on how fluid restriction should be a part of the patient self-care treatment. There is therefore a need for knowledge on how heart failure patients are affected by fluid restriction regarding clincal signs and symptoms of heart failure, quality of life, physical function, readmission to hospital or heart failure events. The primary aim of the study is to investigate whether a free fluid intake is safe compared to a restricted fluid intake, regarding clinical signs of heart failure measured as the presence of B-lines and/or an increase in NT-proBNP. The secondary aim is to clarify whether an unlimited fluid intake can improve quality of life and reduce thirst without affecting heart failure symptoms, physical activity, hospital readmissions and/or heart failure events.

Inclusion Criteria:

• Diagnosed with left ventricual heart failure (HFrEF, HFmEF)
• Physical, cognitive and linguistic ability to carry out all aspects of the study

Exclusion Criteria:

• Reversible cause of HF (thyroid disorders, severe anemia, etc.)
• Hyponatremia at baseline (sodium <130 mmol/L)
• eGFR at baseline <30mL/min/1.73m2
• Scheduled cardiac surgery, coronary intervention (percutaneous coronary intervention or coronary artery bypass graft surgery) within 3 months
• Myocardial infarction within 3 months
• Comorbidity for which fluid restriction or unlimited fluid intake is advised
• Life expectancy <6 months