Stress-induced hyperglycemia is associated with poor outcomes in nearly all critical illnesses. This acute elevation in glucose after injury or illness is associated with increased morbidity and mortality including multiple organ failure. Stress-induced hyperglycemia is often attributed to insulin resistance as controlling glucose levels via exogenous insulin improves outcomes, however, several metabolic derangements likely contribute. Forkhead box O (FOXO) transcription factors regulate glucose homeostasis in the liver via direct and indirect pathways including induction by glucagon, a hormone that is significantly elevated in trauma. Loss of hepatic FOXO transcription factors reduces hyperglycemia in chronic insulin-resistance; however, the role of FOXOs in stress-induced hyperglycemia was unknown. Further, excess glucagon has been implicated in the pathogenesis of Type II Diabetes, but the role of glucagon in stress-induced hyperglycemia including the relevance of its ability to induce FOXO activity is unclear. In the first study, we subjected mice lacking FOXO transcription factors in liver to a model of injury known to cause stress-induced hyperglycemia. We found that loss of FOXO1, 3, and 4 in the liver attenuated hyperglycemia and prevented hyperinsulinemia. Mechanistically, loss of FOXO transcription factors mitigated the stress-induced hyperglycemia response by directly altering gene expression and glycogenolysis in the liver and indirectly suppressing lipolysis in adipose tissue. We then determined if glucagon signaling in the liver was required for stress-induced hyperglycemia, including a potential role for the glucagon-mediated regulation of FOXO’s. In the second study, we used genetic and pharmacological inhibition of the glucagon receptor along with a PKA dominant-negative mutation in the same model of injury as before. Here we found that glucagon is required for stress-induced hyperglycemia. Glucagon’s ability to increase glucose levels after trauma is likely conferred through increased PKA and pIP3R signaling pathways and potentially acute regulation of FOXO to increase hepatic glucose production as demonstrated by our novel combined glucose tracer infusion in trauma method. Future work will determine if successfully lowering glucose levels with pharmacological glucagon blockade translates to reductions in mortality and multiple organ failure in a survival model of trauma. This includes determining whether improvements can be ameliorated by a hyperglycemic clamp, ultimately investigating the role of glucose itself in outcomes after trauma.