Current recommendations for the treatment of abnormal blood glucose levels for stroke rely on evidence-based guidelines. Ongoing advances in neuroimaging, tissue studies, animal studies, and case series and reports present findings that expose additional variables to be considered in the causal analysis of the role of diabetes and glucose control for stroke occurrence and outcome. The physician when treating the individual patient must fold this information into that provided by large clinical trials. Consideration of all information available without limitation to results from large, double-blind randomized trials allows the physician to expect and thus forecast the result of clinical action by understanding the complexity of the situation. Avoiding hypoglycemia and levels of hyperglycemia able to produce symptoms of stroke and cerebral damage by themselves would seem common sense. The plethora of evidence consistent with worse outcome and increased mortality in acutely ill and stroke patients with hyperglycemia also would call for treatment, with prudent avoidance of hypoglycemia. These rules appear to apply for hemorrhage as well as ischemia, and aggressive recommendations for lowing blood glucose caution against hypoglycemia.