Context: Hyperglycemia in hospitalized patients is associated with increased morbidity and mortality. Objective: We examined whether critical illness is more strongly associated with relative or absolute hyperglycemia. Design: The study was an observational cohort study. Patients and setting: 2290 patients acutely admitted to a tertiary hospital. Main outcome measure: Relative hyperglycemia (Stress Hyperglycemia Ratio, (SHR)) was defined as admission glucose divided by estimated average glucose derived from glycosylated hemoglobin.