The nurse is caring for a client with syndrome of inappropriate antidiuretic hormone (SIADH). What diet should the nurse anticipate being ordered by the health care provider?

Syndrome of inappropriate antidiuretic hormone (SIADH) is characterized by the excessive retention of free water due to abnormally elevated ADH secretion, resulting in dilutional hyponatremia. The kidneys reabsorb water despite the body's normal hydration status, causing plasma sodium levels to fall. The primary management strategy is fluid restriction, which limits further water retention and allows sodium levels to gradually normalize. A clear liquid diet does not address the fundamental problem of water excess and could worsen hyponatremia if the fluids consumed are hypotonic. A low sodium diet would be counterproductive because the underlying problem in SIADH is already low serum sodium caused by dilution, not by excess sodium intake. Further restricting sodium intake could deepen the hyponatremia. A consistent carbohydrate diet is used for blood glucose management in diabetes and has no relevance to SIADH. Students sometimes confuse SIADH management with that of diabetes insipidus (DI), which involves the opposite problem — excessive free water loss — and requires fluid replacement. In SIADH, the guiding principle is: the body is retaining too much water, so restrict further intake. Depending on the severity, hypertonic saline may also be administered, but fluid restriction is the anticipated dietary order.