What is the most likely diagnosis for a 53-year-old female with lethargy, fatigue, and dehydration, presenting with a glucose level of 965?

The most likely diagnosis in this scenario is nonketotic hyperosmolar coma, which is also known as hyperglycemic hyperosmolar state (HHS). This condition typically occurs in individuals with type 2 diabetes and is characterized by extremely high blood glucose levels, often exceeding 600 mg/dL, leading to severe dehydration and osmotic diuresis.

The key indicators in this case are the patient's age, symptoms of lethargy and fatigue, and the extremely high glucose measurement of 965 mg/dL. In nonketotic hyperosmolar coma, the body still produces some insulin, which helps prevent the accumulation of ketoacids, distinguishing it from diabetic ketoacidosis (DKA), where there is significant ketosis.

Patients with this condition often present with significant fluid loss due to osmotic diuresis caused by the high glucose levels, leading to dehydration and related symptoms such as lethargy. The hyperosmolar state results from both high blood glucose and the accompanying effects on blood osmolality, which can lead to neurological impairments.

In contrast, other options such as the syndrome of inappropriate antidiuretic hormone secretion and pseudohyponatremia do not match the clinical picture presented. They are not