Summary: Antihypertensive drugs are considered to be safe and well-tolerated. However, in some patients, the use of these drugs may lead to serious side effects. These side effects include hyponatremia caused by thiazide and thiazide-like diuretics (TIH). Hyponatremia induced by thiazide and thiazide-like diuretics is most often deep hyponatraemia, which may manifest itself as symptoms of cerebral edema and lead to coma and death. It can occur in patients treated with any of the medicines in this group. In patients prone to TIH, TIH recurrence after the reuse of thiazide or thiazide-like diuretics is observed. In patients treated with these medicines natremia should be monitored and patients should be informed about the symptoms of TIH and necessity of urgent medical consultation when such symptoms appear. The aim of this paper is to present epidemiological, pathophysiological and therapeutic aspects of hyponatremia caused by thiazide and thiazide-like diuretics.