Malnutrition in the form of insufficient nutrient intake to support tissue metabolism undermines appropriate medical or surgical therapeutic management of a case. The major consequences of malnutrition in all patients are decreased immunocompetence, decreased tissue synthesis and repair, and altered intermediary drug metabolism. A practical goal is to begin nutritional support within 24 hours of the injury, illness, or presentation. There are only two methods by which nutrients can be supplied to the body: enteral and parenteral. General guidelines are presented to help establish a foundation.