It's human nature for people to treat others differently or behave differently around them when they "know" they have been diagnosed with something.
Sometimes it may lead people to have more patience or cut you some slack under circumstances they normally would not have without your diagnosis.
Other people may think you use BiPolar as an "excuse" for any erractic behavior you display and therefore they may elect to spend less time around you. They don't want to deal with any "potential drama".
In the end you have to accept that you are who you are.
You take your meds and do the best you can.
With experience you should be able feel a change coming on. This will help to keep (you) from being caught off guard.
Life is too short to be trying to read other people's minds or to be too worried about what they think.
"Worry does not empty tomorrow of its sorrow. It empties today of its strength." - Corrie Ten Boom
Best of luck!