The hyperglycemic hyperosmolar state (HHS) is a life-threatening medical emergency characterized by severe hyperglycemia, hyperosmolality, and dehydration in individuals with type 2 diabetes mellitus. Unlike diabetic ketoacidosis (DKA), which is more common in type 1 diabetes, HHS typically occurs in older adults with type 2 diabetes who have significant insulin resistance, though it can also occur in type 1 diabetes under certain conditions. The pathogenesis of HHS involves a relative insulin deficiency combined with high levels of counterregulatory hormones such as glucagon, cortisol, and catecholamines, which lead to increased hepatic glucose production and impaired glucose utilization in peripheral tissues. This results in profound hyperglycemia, often exceeding 600 mg/dL (33.3 mmol/L), and osmotic diuresis leading to severe dehydration and electrolyte imbalances. Clinical presentation includes altered mental status, profound dehydration, neurologic symptoms such as seizures or focal deficits, and signs of multiorgan dysfunction. Prompt recognition and management are crucial, focusing initially on fluid resuscitation with isotonic saline to restore intravascular volume and correct electrolyte abnormalities. Insulin therapy is essential to lower blood glucose levels gradually and reverse metabolic abnormalities. Close monitoring of electrolytes, renal function, and cardiovascular status is necessary to avoid complications such as cerebral edema, acute kidney injury, and cardiovascular collapse. Prevention of HHS involves optimizing glycemic control in individuals with type 2 diabetes through regular monitoring, adherence to prescribed medications, and timely medical intervention during periods of illness or stress.