A nurse notices increasing polyuria and high serum glucose in a hospitalized patient. Using critical thinking, what should be the nurse's initial action?

Hyperglycemia induces osmotic diuresis, where high glucose concentrations in the renal tubules prevent water reabsorption. This leads to profound dehydration and solute loss, potentially progressing to hyperosmolar hyperglycemic state or ketoacidosis characterized by severe intracellular and extracellular fluid volume deficits. Rationale: A. Administering insulin without assessing the patient's fluid and electrolyte status is hazardous. Rapidly lowering glucose can cause fluid shifts into the intracellular space, potentially worsening vascular collapse or causing cerebral edema if serum osmolality drops too quickly. B. Assessment of hydration and perfusion is the priority to determine the severity of osmotic loss. Identifying hypovolemia and electrolyte abnormalities like hypokalemia is essential before initiating treatments that further shift potassium into cells or increase urinary output. C. While exercise can enhance insulin sensitivity, it is inappropriate and dangerous for an acutely symptomatic hospitalized patient. Physical exertion during severe hyperglycemia can actually increase ketone production and worsen metabolic stress or cardiovascular strain in unstable patients. D. Nutritional counseling is a long-term preventative strategy rather than an acute intervention. In the presence of polyuria and significant hyperglycemia, the nurse must focus on acute stabilization and physiological monitoring rather than lifestyle education which requires cognitive readiness.