THIAZIDE - A group of medications that cause diuresis (loss of water through the kidney). They are frequently used to treat high blood pressure and congestive heart failure. Thiazides can cause low blood potassium levels if dietary potassium or (a potassium supplement) is not taken. Thiazides include hydrochlorothiazide, methyclothiazide, chlorthalidone, bendroflumethiazide, hydroflumethiazide, polythiazide, trichlormethiazide, and chlorothiazide.