Since one gram of protein in food provides approximately 15 mg of phosphorus, phosphorus deficiency frequently observed in patients with protein-energy malnutrition (PEM). Chronic phosphorus deficiency in humans causes proximal myopathy. Acute hypophosphatemia may precipitate rhabdomyolysis. Plasma low phosphorus concentration suppresses erythrocyte synthesis and stores of 2,3-diphosphoglycerate (2,3-DPG) , which plays an important role in the affinity of hemoglobin for oxygen. Symptoms of nervous system dysfunction, such as weakness, apathy, a bedridden state, and intention tremors, are also observed in severe hypophosphatemia. Refeeding syndrome is caused by rapid refeeding in PEM, characterized by hypophosphatemia and has metabolic and clinical complications. This is potentially fatal, yet is preventable. Awareness and identification of at-risk patients is crucial to improving management.