one standard deviation below the mean using standard growth charts, which include the World Health Organization (WHO) charts for patients younger than years old and the Centers for Disease Control (CDC) charts for patients years and older Pediatric malnutrition in children years and older can also be defined as body mass index (BMI) greater than one standard deviation below the mean A z-score can be calculated, which represents the number of standard deviations away from the mean Z-scores of a measure such as weight-for-age can help to classify pediatric malnutrition as mild (z-score, −1 to −1.99), moderate (z-score, −2 to −2.99), or severe (z-score, ≤−3) Of note, on the WHO charts for children to years of age, a weight-for-age or weight-for-length z-score of −2 corresponds approximately to the second percentile Many available computer programs as well as many electronic medical records can readily generate z-scores from a patient’s anthropometric data Failure to thrive is often defined as a child’s weight dropping major percentiles on an appropriate growth chart (using the 90th, 75th, 50th, 25th, 10th, and 5th percentiles) Failure to thrive can also be defined as a decline in a weightfor-age or weight-for-length z-score by more than 1, which should prompt further evaluation and management Assessment of weight loss should begin with an accurate measurement of a patient’s weight and height using accurate technique and equipment Recumbent length should be measured in patients younger than years and standing height should be measured in patients years and older Head circumference should also be measured in patients younger than These measurements should be plotted on appropriate standardized growth charts to generate z-scores Anthropometric percentiles may also be calculated, although z-scores give a more precise measure of the severity of malnutrition and allow better tracking of changes in malnutrition over time Of note, medical providers should use corrected age for former premature infants until years of age The emergency provider should determine if the patient is presenting with acute weight loss (5% to 10% of body weight) should raise concern for life-threatening disorders that require prompt recognition and treatment Acute weight loss is most often caused by decreased fluid and caloric intake, increased losses (such as via diarrhea and vomiting), or increased metabolic requirements in association with an acute illness The history should include an estimation of intake and losses The types of losses (e.g., urine, stool, or emesis) may pinpoint the location and etiology of the pathology