Undernutrition is often overlooked in efforts to deal with obvious presenting complaints. Correcting malnutrition is worthwhile—it has significant deleterious effects on musculoskeletal, gastro-intestinal and cardiorespiratory function, the immune system and even mood. In patients who have lost more than 20% of body weight, nutritional support has been shown to reduce postoperative complications. However, there is no fail-safe method to identify malnourished patients. Most hospitals now use some type of nutritional screening tool (Figure 1), a form completed by the admitting nurse.