Refeeding syndrome is a medical complication following a prolonged period of malnutrition or starvation, when rapid intake of food and fluids creates electrolyte imbalances that can result in multiorgan dysfunction and can be fatal. This can occur with both enteral and parenteral nutrition and usually happens within the first 2 weeks of nutritional replenishment. It is characterized by hypophosphatemia, hypokalemia, hypomagnesemia, thiamine deficiency, peripheral edema, arrhythmias, and congestive heart failure.

History of anorexia nervosa, alcohol use disorder, chronic malnutrition (short bowel syndrome, inflammatory bowel disease, chronic pancreatitis, cystic fibrosis, morbid obesity with profound weight loss, prolonged fasting), or uncontrolled diabetes confer a risk of refeeding syndrome. In addition, elderly patients, long-term antacid users, long-term diuretic users, oncology patients, and postoperative patients with prolonged nothing-by-mouth (NPO) status are at increased risk. Both children and adults can be affected if they have any of the above ailments. Those most at risk have lost greater than 70% of their ideal body weight or have a body mass index (BMI) less than 15 kg/m². Higher BMI, normal potassium levels, and normal prealbumin decrease the risk of refeeding syndrome.

Initial signs and symptoms in adults include palpitations, peripheral edema, weakness, diarrhea, tremors, and dyspnea. Delirium usually occurs during the second week of refeeding syndrome. Seizures and hemolysis can also manifest due to severe electrolyte derangements. Rhabdomyolysis can occur in this setting with elevated creatinine kinase (CK) leading to renal dysfunction. Diarrhea occurs in the setting of intestinal atrophy and pancreatic insufficiency, which typically resolve after a few weeks. Children with refeeding syndrome can present with fever, hepatomegaly, sweating, widening of sutures, lethargy, hyperactivity, and fussiness.

Mortality from refeeding syndrome is linked to consequences of electrolyte abnormalities and heart failure. Treatment entails controlled refeeding and close monitoring of electrolytes and vital signs in a controlled environment as nutrition is being introduced. Prevention of refeeding syndrome is done by avoiding rapid increases in daily caloric intake in at-risk patients.