Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) are severe and potentially life-threatening complications of diabetes that can develop in those diagnosed with diabetes. Based on published data from CDC in 2021, 38.4 million people in the USA had diabetes (11.6% of the population). In 2020, among 267,000 emergency department (ED) visits related to the hyperglycemic crisis, 84.4% needed hospital admissions with a <0.1% mortality rate (Centers for Disease Control and Prevention, National Diabetes Statistics Report, https://www.cdc.gov/diabetes/data/statistics-report/index.html , Accessed 14 Mar 2024). Patients with a diagnosis of diabetes, receiving intravenous or oral glucose-lowering agents are at risk for hypoglycemia. The purpose of this book chapter is to provide an overview of these emergencies individually and discuss the potential overlap in both disease states and clinical presentations that can occur in this patient population.