Malnutrition is the gravest single threat to the world’s public health. Approximately 27% of children under five years in developing countries are malnourished and in developing countries malnutrition claims about half of the death each year of children under five years. Re- feeding after a prolonged period of fasting or starvation can result in a serious complication. This potentially lethal condition can be defined as severe fluid and electrolytes shift associated with metabolic abnormalities in malnourished. The biochemical hallmark of this syndrome is hypophosphataemia in addition to other electrolytes disturbance like potassium and magnesium with or without derangement in serum glucose. The incidence of re-feeding syndrome is unknown largely because no accepted definition exists Doctors and other health care providers should be aware of patients at risk of re-feeding complications. As well as clinical status must be monitored carefully during re-feeding especially vital signs (heart rate and respiratory rate) as well as Monitoring serum phosphate, potassium, magnesium and glucose before and during re-feeding.