Abstract
BACKGROUND: Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) are life-threatening acute complications of diabetes. Up to one-third of patients present with overlapping features of both syndromes, complicating diagnosis and management. This overlap is associated with higher mortality than isolated DKA or HHS. OBJECTIVE: This narrative review synthesizes current evidence on the epidemiology, pathophysiology, and management of DKA-HHS overlap in both adult and pediatric populations with either type 1 or type 2 diabetes, highlighting the distinct challenges in recognition, treatment, and outcomes across these groups. FINDINGS: While DKA is defined by ketosis and metabolic acidosis, and HHS by profound hyperglycemia and hyperosmolality, overlap presentations combine both abnormalities. These patients face increased risks of cerebral edema, thromboembolism, and acute kidney injury. Standardized management protocols remain lacking, and treatment must balance fluid resuscitation, insulin therapy, and electrolyte correction, with distinct approaches for adults and children. Emerging issues such as SGLT2 inhibitor-induced euglycemic DKA and disparities in outcomes between high- and low-resource settings further complicate care. CONCLUSION: DKA-HHS overlap represents a high-risk clinical phenotype requiring early recognition and individualized therapy. Consensus guidelines, risk stratification tools, and studies of fluid and insulin strategies are urgently needed to improve outcomes in this vulnerable population.