Diuretics act in the kidneys. They work by causing the kidneys to increase the amount of salts, such as potassium and sodium, that are filtered out of the blood and into the urine. When these salts are filtered out of the blood by the kidneys, they draw water alongside them. As diuretics increase the removal of salts from the blood, they also cause more water to be drawn out of the blood and into the urine. Removing water from the blood decreases the volume of fluid circulating through the blood vessels. This subsequently decreases the pressure within the blood vessels. Diuretics such as hydrochlorothiazide and amiloride can therefore be used to lower high blood pressure.