As someone mentioned, there are many many 'flavors' of BP (I and II). But my feeling has always been that if one's moods flip from one end to the other in a matter of hours, then we should start thinking of the possibility of Borderline Personality Disorder. I don't want to venture a diagnosis for anyone who experiences this, but it's something to consider. You can find the criteria on-line, which requires a lot more than quick mood swings, but you can get a pretty good idea if you fit the criteria and then bring that into an appointment with your T and/or Pdoc and see if they agree. Pdocs and T's can be loathe to diagnose BPD because of all of the stigma, but if you're proactive (and you suspect it), you can have a conversation with them, and as I said, see if they agree. You can, of course, have both BP and BPD at the same time.