The refeeding syndrome may occur during reintroduction of carbohydrates in malnourished patients. This syndrome is characterized by reduced plasma electrolyte levels, hypophosphataemia being most prevalent. The symptoms can vary from minor symptoms to severe neurological or cardiac symptoms. The pathophysiological mechanism comprises an increase in insulin levels, resulting in shifts of phosphate, potassium and magnesium into the intracellular environment, as well as fluid retention and relative deficiency of vitamin B1. There is growing interest in the screening and treatment of patients with malnutrition, due to which the incidence of refeeding syndrome is probably increasing. Currently, there is no single definition of this syndrome and therefore there is no solid scientific basis for screening and treatment. In this article we describe the rationale for screening and additional laboratory investigations. A prospective, controlled trial is important to define the clinical relevance of the refeeding syndrome and optimize its treatment.