Diabetes mellitus causes profound alterations in nutrient metabolism, leading to long-term systemic complications, particularly in individuals with poorly controlled disease. Nutrition support clinicians need to be aware of the effect of acute illness on stress-induced and established diabetes mellitus and the appropriate management strategies. Because enteral feeding is a vital component of critical care for many patients with diabetes mellitus, it is important to develop techniques to best manage metabolic control during enteral feeding. This article will review mechanics of blood glucose regulation, evaluation of energy sources for patients with diabetes mellitus, selection of enteral formulas and infusion routes, and glycemic control in patients receiving tube feeding. At this point, it is appropriate to use a standard formula to initiate feedings in most patients with blood glucose abnormalities. Close monitoring and judicious use of insulin are key in maintaining glucose control and avoiding complications.