Rationale: A. Assess the heart rate frequently: While changes in fluid volume can affect heart rate, monitoring heart rate alone does not provide a direct measure of desmopressin’s effectiveness in controlling diabetes insipidus. Heart rate may remain normal even if polyuria persists. B. Check for daily bowel movement: Desmopressin primarily affects water reabsorption in the kidneys and does not influence gastrointestinal motility. Monitoring bowel movements does not reflect the therapeutic effect of the drug in diabetes insipidus. C. Review the serum glucose level: Serum glucose levels are relevant in diabetes mellitus, not diabetes insipidus. Desmopressin’s action is unrelated to glucose metabolism, so checking glucose does not assess its effectiveness. D. Measure the intake and output: Desmopressin acts as a synthetic antidiuretic hormone, reducing urine output and promoting water reabsorption. Tracking fluid intake and urine output allows the nurse to determine if polyuria is resolving and fluid balance is being maintained, directly reflecting the drug’s therapeutic effect.