Thirst is a common and troublesome symptom for patients with moderate to severe heart failure. The pharmacological and non- pharmacological treatment as well as the nature of the disease itself causes increased thirst. There is no evidence in the literature about the usefulness of fluid restriction for heart failure patients. Formerly, when very little pharmacological treatment was available, fluid restriction was one of the few interventional options but nowadays when the pharmacological treatment has improved, its importance may be questioned. This article describes the design of an ongoing study with the aim to determine if an individualised and less restrictive fluid prescription can improve the quality of life, cardiac function and exercise capacity, and decrease in hospital admissions and thirst. This study will be performed as a two-group, 1:1 randomised cross-over study. In group 1, the patients are instructed to comply with a maximum fluid intake of 1.5 l. This is a standard treatment today. In group 2, the patients are recommended to intake a fluid, based on the physiological need of 30 ml/kg body weight/24 h, and are allowed to increase the fluid intake to a maximum of 35 ml/kg body weight/24 h. After 16 weeks, the patients will cross over to the other intervention strategy and continue for another 16 weeks.