Complications of enteral nutrition support in critically ill patients include mechanical complications, respiratory complications, intestinal complications, and metabolic complications. Mechanical complications include pharyngeal irritation and mucosal damage caused by overly thick catheters and hard materials, as well as blockage of the nutrition tube and catheter displacement. Respiratory complications include aspiration and pulmonary infection, and occur in coma, catheter position, and poor gastric emptying, especially in patients who have undergone esophageal and gastric surgery and have altered anatomy. Gastrointestinal complications may include nausea, vomiting, bloating, intestinal cramps, hyperperistalsis, diarrhea, and gastric retention, and may be related to inappropriate nutritional product formulation choices or inappropriate infusion concentrations and rates. Metabolic complications include hyperglycemia, hypoglycemia, ketotic hyperosmolar coma, electrolyte disturbances, and nutrient deficiencies or excesses.