A nurse is caring for a client who has diabetes insipidus and is receiving vasopressin. The nurse should identify which of the following findings as an indication that the medication is effective?

A. A decrease in blood sugar: Vasopressin does not directly affect blood sugar levels. It is used to treat diabetes insipidus by reducing urine output, not by affecting glucose metabolism. B. A decrease in blood pressure: Vasopressin can have vasoconstrictive effects, but the primary goal in diabetes insipidus is to reduce excessive urine output. Blood pressure changes are not a key indicator of the medication's effectiveness in this condition. C. A decrease in specific gravity: Specific gravity would increase with effective vasopressin therapy, as it helps the kidneys concentrate urine, making it more concentrated, not less. D. A decrease in urine output: The effectiveness of vasopressin is demonstrated by a decrease in urine output. Vasopressin helps the kidneys retain water, reducing the excessive urination characteristic of diabetes insipidus.