Well, while I echo what everyone else has said regarding online tests, I know where you're coming from as I did the same thing. I knew something was wrong with me mood wise, so I stumbled across this place and also scored high on the bipolar test.

I got up the nerve to see a therapist, who told me recently he's pretty positive I have cyclothymic disorder. So, I'm on the bipolar spectrum, but not as severe as the tests would have me believe (they said I likely had bipolar I).

These tests are more a tool to let you know if you should be concerned. If you feel like you can't function normally in life, definitely see a therapist / psychiatrist so you can get a more professional and thorough analysis.