can you be fired for a medical condition at dollar tree?

I live in ohio and I have worked at dollar tree in ohio and have been for over 4 years. I have epilepsy and my boss has known that since before I started. Sometimes I need to take time off work because of my seizures and reasons stemming from them (I can't get a ride, which is rare). My boss has told me repeatedly that I can be fired because I'm a liability, and that I should have been gone a long time ago because of the shifts I've had to call off, or the hours I've lost from having a seizure at work and having to leave and not being able to work for 1-2 days afterwards.