What Is The Treatment For Frequent Urination And What Causes White Film In Mouth While Speaking?

Question : My dad is 68 years old normally spry, goes to the gym and functions perfectly. For the past three weeks he has had frequent urination( so bad he wets the bed and can't be out the house for too long), he says he can still taste the soup I gave him when he was stuck in the bed the first weeks he was sick, I see a white film in his mouth when he speaks (not sure if dehydration 'cause he doesn't drink as much water as he should due to the frequent urination), his feet were swollen more than usual for a couple weeks and a week ago his leg started to swell going down a little now, he's tired easily, he's cold so he keeps the heater on all day, he has tremors when he exerts himself and shakes when he gets too cold, some constipation, and to me his ability to think and respond is delayed-some of the things he says don't make sense in the context of the conversation. He's a firm believer in natural health so he doesn't want to see a medical doctor and consults with a doctor who focuses on nutrition, I just want to make sure it's not something serious.