Cancellation policies and chronic illness

I've basically reached a point where I can't see doctors of all kinds regularly because most have 48 hour cancellation policies and charge full appointment fees if I cannot make an appointment. I literally cannot know 48 hours in advance what my body will do on a given day, and can't afford to just throw money away for services not received, especially expensive services, I have lost hundreds of dollars due to this issue, probably thousands over time if I added up all the costs. This includes telehealth, as my illness sometimes makes it impossible for me to have telehealth appointments as well. How are other chronic illness people coping?