Hyperglycemic crises in adult patients with diabetes include diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), the two most serious acute metabolic complications. DKA is responsible for over 500,000 hospital days annually and has a mortality rate of less than 1% in adults, though it is higher in the elderly and those with comorbid conditions. HHS has a higher mortality rate (5–20%) and is associated with severe dehydration and hyperglycemia. Both conditions are more common in younger adults and are often linked to infections, trauma, or surgery. DKA is most common in type 1 diabetes, but type 2 diabetes patients are also at risk during acute illness. HHS is more common in non-diabetics and is associated with severe dehydration due to osmotic diuresis. DKA is characterized by hyperglycemia, metabolic acidosis, and elevated ketone levels, while HHS is marked by severe hyperglycemia, hyperosmolality, and dehydration without significant ketoacidosis. Both conditions result from insulin deficiency and increased counterregulatory hormones. DKA is often caused by infections, inadequate insulin therapy, or new-onset type 1 diabetes, while HHS is associated with dehydration and lack of access to water. Treatment of DKA and HHS involves correcting dehydration, hyperglycemia, and electrolyte imbalances, along with identifying and managing underlying causes. Fluid resuscitation with isotonic saline is typically initiated, followed by insulin therapy to lower blood glucose and ketones. Insulin therapy is effective regardless of administration route, with continuous intravenous infusion being preferred. Potassium replacement is necessary to prevent hypokalemia, and bicarbonate therapy is controversial due to potential risks. Prevention strategies include better access to medical care, patient education, and effective communication with healthcare providers during illness. Education on sick day management, proper insulin use, and early recognition of symptoms can help prevent DKA and HHS. Home glucose and ketone monitoring can aid in early detection and management. Addressing socioeconomic and cultural barriers to care is essential for reducing DKA and HHS incidence, particularly in high-risk populations.Hyperglycemic crises in adult patients with diabetes include diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), the two most serious acute metabolic complications. DKA is responsible for over 500,000 hospital days annually and has a mortality rate of less than 1% in adults, though it is higher in the elderly and those with comorbid conditions. HHS has a higher mortality rate (5–20%) and is associated with severe dehydration and hyperglycemia. Both conditions are more common in younger adults and are often linked to infections, trauma, or surgery. DKA is most common in type 1 diabetes, but type 2 diabetes patients are also at risk during acute illness. HHS is more common in non-diabetics and is associated with severe dehydration due to osmotic diuresis. DKA is characterized by hyperglycemia, metabolic acidosis, and elevated ketone levels, while HHS is marked by severe hyperglycemia, hyperosmolality, and dehydration without significant ketoacidosis. Both conditions result from insulin deficiency and increased counterregulatory hormones. DKA is often caused by infections, inadequate insulin therapy, or new-onset type 1 diabetes, while HHS is associated with dehydration and lack of access to water. Treatment of DKA and HHS involves correcting dehydration, hyperglycemia, and electrolyte imbalances, along with identifying and managing underlying causes. Fluid resuscitation with isotonic saline is typically initiated, followed by insulin therapy to lower blood glucose and ketones. Insulin therapy is effective regardless of administration route, with continuous intravenous infusion being preferred. Potassium replacement is necessary to prevent hypokalemia, and bicarbonate therapy is controversial due to potential risks. Prevention strategies include better access to medical care, patient education, and effective communication with healthcare providers during illness. Education on sick day management, proper insulin use, and early recognition of symptoms can help prevent DKA and HHS. Home glucose and ketone monitoring can aid in early detection and management. Addressing socioeconomic and cultural barriers to care is essential for reducing DKA and HHS incidence, particularly in high-risk populations.