Continuous glucose measurement would facilitate blood glucose control in critically ill patients. Numerous studies have shown accuracy of the subcutaneous continuous glucose monitoring derived glucose values compared to blood glucose measurements in diabetics. Studies evaluating the subcutaneous continuous glucose monitoring in an inpatient-population especially in an ICU-setting are rare. Therefore the aim of this study is the prospective evaluation of continuous subcutaneous glucose monitoring in critically ill patients with circulatory shock demanding norepinephrine therapy as compared to critically ill patients without shock.