The diagnosis of SIADH involves a combination of clinical evaluation and laboratory tests. Key diagnostic criteria include:
Hyponatremia with serum sodium < 135 mmol/L Low serum osmolality < 275 mOsm/kg Urine osmolality > 100 mOsm/kg Euvolemia (normal blood volume without signs of dehydration or fluid overload) Normal renal, adrenal, and thyroid function
