Depending on the extent of the blood potassium level and underlying kidney or adrenal gland condition at the time of diagnosis, the prognosis of hypoaldosteronism may vary.   
Prognosis is generally good for patients of hypoaldosteronism who receive treatment. Untreated patients risk having increased blood potassium level which leads to abnormal electrical conduction in heart that can be fatal. Patient having underlying renal disease or diabetic nephropathy may progresses to end stage stage renal disease.
What to expect if I have Hypoaldosteronism  (Outlook/Prognosis)?
Depending on the extent of the blood potassium level and underlying kidney or adrenal gland condition at the time of diagnosis, the prognosis of hypoaldosteronism may vary.   
Prognosis is generally good for patients of hypoaldosteronism who receive treatment. Untreated patients risk having increased blood potassium level which leads to abnormal electrical conduction in heart that can be fatal. Patient having underlying renal disease or diabetic nephropathy may progresses to end stage stage renal disease.