Nocturnal polyuria (NP) is a condition characterised by excessive nocturnal urine production, accounting for over a third of daily urine output in individuals over 65 years of age. The pathophysiology of NP is involves cardiovascular, renal, and hormonal organ systems, with a key role played by arginine vasopressin (AVP), which stimulates water resorption in the kidneys. In NP, the circadian regulation of AVP is disrupted, leading to increased night time urine production and nocturia. Desmopressin, a synthetic analogue of AVP, is used in the management of NP. Desmopressin selectively binds to V2 receptors in the renal collecting ducts, enhancing water reabsorption and reducing nocturnal urine volume. Tailored dosing minimises adverse effects, particularly hyponatremia, a common side effect due to its antidiuretic action. Careful monitoring of sodium levels is required, particularly in elderly patients and those with renal impairment.