More than 30% of general hospital inpatients experience episodes of hyperglycemia. These individuals suffer more in-hospital complications, longer stays, and higher treatment costs. To prevent these adverse effects, many hospitals, including the applicant institution, have introduced physiologic insulin treatment protocols (also referred to as basal-bolus therapy) intended to maintain blood glucose within a specified range. Physiologic insulin therapy includes multiple daily injections to cover insulin needs: basal (overnight fasting and between-meal), prandial (glucose excursions above basal at mealtime), and correction (supplemental insulin, as needed to correct hyperglycemia). Current national guidelines recommend physiologic insulin- and discourage a traditional sliding scale regimen (correction component only) or oral agents-but the guidelines note that beneficial effects of the therapy on clinical outcomes and hospital resource use have not been proven in the general inpatient setting. A recent systematic review of the pertinent literature came to the same conclusion, emphasizing the need for further research before routinely incorporating intensive forms of glycemic control in a general inpatient population. Since strategies to control hyperglycemia lead to potentially dangerous episodes of hypoglycemia in 1 of every 12 inpatients, sometimes causing seizures, coma, brain injury, or death in severe cases, it is critically important to demonstrate the benefits of this approach before accepting it as a hospital wide standard of care. The primary aim of the proposed study is to determine if physiologic insulin therapy administered to general hospital in patients with hyperglycemia favorably affects in-hospital complications and mortality, need for intensive care, or length of stay. The secondary aim is to determine if the magnitude of benefit derived from this therapy differs (a) in patients with known vs. newly diagnosed diabetes, or (b) in medical vs. surgical patients. The study will analyze data from a natural experiment that occurred when the applicant institution introduced universal physiologic insulin therapy as the standard of care for hyperglycemia. A quasi-experimental before-and-after study will compare in-hospital complications, mortality, and resource use in patients with comorbid type 2 diabetes before vs. after implementation of this standard (n~6400). Outcomes measured at 7 nearby acute-care teaching hospitals during the same two time intervals will provide parallel control data (n~35,000). Data from the control hospitals will make it possible to evaluate whether temporal changes in patient characteristics or other variables affecting hospitals in the region could explain effects that might otherwise be erroneously attributed to the intervention. Given the high prevalence of comorbid diabetes in the hospital and the possibility that universal physiologic insulin for managing hyperglycemia may not deliver the intended benefit or could even do more harm than good, answering this question is an important goal.