Relationships between blood glucose concentration and outcome and also the optimum management of blood glucose remain highly contentious issues for critical care practitioners. Among the many controversies is whether critically ill patients with diabetes should be treated differently from those without diabetes. Krinsley and colleagues assembled a large observational database that sheds further light on the relationships of hyperglycemia, hypoglycemia and glucose variability and risk of death in critically ill patients with and without diabetes. Defining the optimum treatment and whether this should differ by diabetic status requires high-quality primary interventional research.