You might want to research the Americans With Disabilities Act (ADA). Bipolar disorder is a covered condition under the ADA, and your employer is obligated to provide you with reasonable accommodations so you can perform your job adequately and safely. The downside to this is that you have to disclose your reasons for needing the accommodations, but it's incumbent on them to work with you instead of disciplining you once you disclose.

I recently had to disclose my BP to my employer because of a similar scenario---I'd been making a lot of mistakes and forgetting to follow up on things, pissed off a couple of my residents' family members by not using the filter I usually utilize when dealing with obnoxious people. Luckily, I have a very understanding boss who 'gets it' and even runs interference for me when I'm having a horrible day; but not everyone is as fortunate as I, which is why the ADA is in place today.