Acute hyperglycemic emergencies are a common cause of diabetes-related hospitalization. Diabetes ketoacidosis (DKA) is typically seen in patients with type 1 diabetes, and hyperosmolar hyperglycemic state (HHS) is typically seen in patients with type 2 diabetes. Presentation of DKA is acute with polyuria, polydipsia, and abdominal symptoms and characterized by hyperglycemia, ketonemia, and anion gap metabolic acidosis. Presentation of HHS is subacute with symptoms similar to DKA followed by altered mental status and extremely high blood glucose levels with high plasma osmolarity. Euglycemic DKA (EDKA) is a more gradual but not less severe complication of diabetes with an incidence increasing in the setting of SGLT-2 inhibitor use. The most common precipitating causes of acute hyperglycemic emergencies include medication nonadherence, infections, and ischemic events. The key to treatment, for both DKA and HHS, is rehydration, insulin therapy, and electrolyte management. With proper treatment, mortality from acute hyperglycemic emergencies has been decreasing, but the morbidity is still very high.