Potassium is found naturally in many foods, such as prunes, apricots, sweet potatoes, and lima beans. But food may not be enough to keep up your potassium levels if you take a diuretic for high blood pressure such as hydrochlorothiazide. These drugs cause potassium to leave your body in the urine, thereby lowering your body's potassium levels. At least a third of patients on diuretics for heart failure or high blood pressure or edema don't get enough potassium from their diets. In those cases, we do use supplements. Don't try a supplement on your own. Too much potassium, like too little, can lead to dangerous irregular heart rhythms.