Objective: To investigate glycemic dynamics and its relation with mortality in critically ill patients. We searched for differences in complexity of the glycemic profile between survivors and nonsurvivors in patients admitted to a multidisciplinary intensive care unit.Design: Prospective, observational study, convenience sample. Settings: Multidisciplinary intensive care unit of a teaching hospital in Madrid, Spain.Patients: A convenience sample of 42 patients, aged 29 to 86 yrs, admitted to an intensive care unit with an Acute Physiology and Chronic Health Evaluation II score of >14 and with an anticipated intensive care unit stay of >72 hrs.Interventions: A continuous glucose monitoring system was used to measure subcutaneous interstitial fluid glucose levels every 5 mins for 48 hrs during the first days of intensive care unit stay. A 24-hr period (n = 288 measurements) was used as time series for complexity analysis of the glycemic profile. n recent years, there has been a growing interest in hyperglycemia associated with critical illness. Hyperglycemia in critically ill patients is a consequence of several factors, including increased cortisol, catecholamines, glucagon, growth hormone, gluconeogenesis, and glycogenolysis (1, 2). In addition, insulin resistance has been demonstrated in >80% of critically ill patients (3).