Aldactone (spironolactone) is a potassium-sparing diuretic (water pill) that prevents your body from absorbing too much salt and keeps your potassium levels from getting too low. Aldactone is used to diagnose or treat a condition in which you have too much aldosterone in your body. Aldosterone is a hormone produced by your adrenal glands to help regulate the salt and water balance in your body. Aldactone also treats fluid retention (edema) in people with congestive heart failure, cirrhosis of the liver, or a kidney disorder called nephrotic syndrome. This medication is also used to treat or prevent hypokalemia (low potassium levels in the blood). While using Aldactone, you may need frequent blood tests. Aldactone cause unusual results with certain medical tests. Tell any doctor who treats you that you are using this medicine. If you need surgery, tell the surgeon ahead of time that you are using Aldactone. You may need to stop using the medicine for a short time. If you are being treated for high blood pressure, keep using this medication even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.