Copper is an essential nutrient for humans. Copper is a component of numerous enzymes that affect a wide variety of metabolic processes. Copper deficiency can result in anemia, neutropenia, skeletal abnormalities, and other clinical manifestations. There is no well-established laboratory measurement of body copper status. Copper supplementation is essential in parenteral nutrition to prevent an adverse effect of deficiency. Balance studies indicate that copper requirements in total parenteral nutrition amount to 0.3 mg/day in the adult. For children and infants, the estimated requirement is 20 microg/kg body wt/day. These amounts may have to be decreased in patients with cholestasis.