Persistent fatigue. Erythropoietin or as it is also known EPO is very important for our organism and influences our mood. And your kidney is producing it all the time. In case your kidney is diseased, your mood can become gloomy, and you may feel a persistent fatigue. Be careful as it is one of those symptoms people always ignore and links to something else. Your kidney produces EPO less than it should, and your blood does not receive enough red blood cells.