Hello, and Welcome to Allnurses!
I'm a longtime member here who also happens to have rapid-cycling bipolar 1. I got through most of my career undiagnosed (didn't find out till a little over 2 years ago) but struggled badly with nursing jobs. Ironically, I was the most stable when I was working straight nights, although aging eventually made it all but impossible for me to do nights anymore.
My psychiatrist puts it this way: SOME people with bipolar can work nights, IF they are stable and IF they stick strictly to a night schedule, even on their days off. It's when you go back and forth between days and nights that you're more apt to decompensate. Since you're not on medications, you don't have to worry about taking them at the same time(s) every day; the trick is to make sure you are getting adequate sleep and that you sleep on a schedule.
Make sure your room is dark and quiet (blackout curtains and white noise from a fan help more than you'd think), turn your phone off, and instruct everyone you live with that your sleep time is not
to be interrupted unless the house is on fire. A warm bath or shower 30-45 minutes or so before going to bed also helps trick your body into thinking it's time for sleep.
You may do fine with nights. You won't know until you try. I wish I COULD work nights, because I am not a morning person and I can't handle all the distractions of day shift, e.g. ringing phones, families, "suits", new orders, doctors, prepping pts for surgery etc. But my nursing career has taken several hits due to my mental health, so I'm not working at all right now, and I've stopped looking for nursing jobs so I may not be the best person to advise you. I hope some other BP nurses here who are currently practicing will stop by and offer you their perspectives.
Wishing you the very best.