Acute kidney injury (AKI) is a frequent complication affecting many hospitalized patients and is associated with increased morbidity and mortality. AKI seldom occurs as isolated organ failure; much more often it emerges as a component of the multiple organ failure syndrome, within the framework of the severe-prolonged catabolic phase determined by critical illness. Patients with AKI often have protein-energy wasting, which represents a major negative prognostic factor. Malnutrition in AKI patients is associated with increased risk of complications, longer hospitalization, and higher hospital mortality. Hence, appropriate nutritional support is essential in the management of the AKI patient. Assessment of nutritional requirements should take into account the patient’s underlying disease, comorbid medical conditions, severity of the renal dysfunction and need for RRT. The primary goals of nutritional support in AKI are the same as those suggested for critically ill patients with normal renal function: to ensure the delivery of adequate amounts of nutrients, to prevent protein-energy wasting with the attendant metabolic complications, to reduce mortality. Since AKI comprises a highly heterogeneous group of subjects with nutrient needs widely varying even along the clinical course in the same patient, nutritional requirements should be frequently reassessed, individualized and carefully integrated with RRT..