Background: Deviations in glucose control in critical care have been shown to increase mortality and morbidity. However, optimal glucose control through present technologies has shown to be a challenge. The insulin balanced infusion system (IBIS) is a new and emerging technology. Methods: The closed loop system was tested in a stress trial to evaluate glucose stability in response to various conditions in nonrandomized people with type 1 diabetes mellitus (n=12). The prototype used in this trial was based on intermittent capillary measurements. Results: Induced stresses in the study using unpredicted stimuli of intravenous or oral glucose and intravenous insulin boluses, was contained with glucose remaining in target 43.8% of the time. Mean increase in glucose concentration after glucose load was 17.4 mg/dl; after insulin bolus, no hypoglycemia (blood glucose less than 70 mg/dl) occurred. Conclusion: The use of IBIS proved safe and feasible under a wide range of conditions. The sensing and stress response of the IBIS demonstrated noticeable features.