What’s the best way to talk to a boss about your mental illness?

Hey I’m working at a restaurant while I get back on my feet after having issues holding down jobs due to my Bipolar diagnosis. I really like it and it’s been good so far, but I can feel myself cycling low again and when I do I often go days without sleep. During those days I’m in active psychosis and I’m not a dream to be around. How do I explain to my boss that this happens and i can’t control it?