To answer your first 2 questions: I'm too nervous to tell my boss, so I've never told him. He's noticed my mood swings and has yelled at me for my "fluctuations in performance". I think if he knew what was really going on, I could possibly be fired.

I guess if it came down to it, I would do like wildflowerchild and say I have depression. I would never admit to having BP. However, that's just me given my situation and my asshole boss.

To answer your last 2 questions: It's ultimately up to you to tell your boss, but people do unfortunately lose their jobs over this type of disclosure. While it is illegal to fire someone for having an MI, your boss could say he's firing you for a BS reason, and there's not much you can do about it. So just be aware of that. For example, your boss knows you were about to snap at that patient, which means he could accuse you of being a "danger" to patients (or some f***ed up reason like that).

On the upside, your boss could be totally understanding and give you some leeway. It could go either way. I would consider how good you get along with your boss, how long you've worked there, and what kind of person your boss is.