I'd be concerned. When I use to feel this way in the past it was a sign of approaching paranoia. As for "on the upside of things" perhaps you mean hypomanic. I know when people experience depression they sometimes don't want to be around people but I'd say there might be more going on here. You might want to speak to your psychiatrist about this. I would never attempt to provide a diagnosis but although schizoaffective disorder which I have is easy to tell some people here have posted they have bipolar with psychotic features. You might want to ask your psychiatrist more about that as some antipsychotics are used as mood stabilizers as well. Most of the people I know with straight bipolar in manic episodes have the need to be around people all the time and can't focus on things. Avoiding people might show something else. I'd suggest you think about what else might be going on in your life and have a good conversation with your psychiatrist and see if that might help but do discuss it.
I think it's common to alienate people, especially when you're first trying to wrap you're brain around the idea of being "bipolar". It's hard to want to be around or talk to people who could have no possibly way of knowing what it is you go through and feel. . . that being said I think it's important not to alienate those very people. Many give good examples of stable moods and of loving environments that you should hold on to. I know I sound a little Mary Poppins here but I went through the same thing aboout 9 months ago. I didn't even want to ADMIT what i had much less talk to people about it or be around anyone that didn't also have it. All this time later i have better stronger relationships with my boyfriend and best friends...
P.s. This isn't the only time I alienate people. I do it quite frequently and my friends are used to it, but I think this time it's the icing on the cake. They don't care anymore. Oh well. I don't even care