I don't tell people, when I do I say I have bipolar, they act akwardly because I don't have the stereotpyed symtoms of hypersexuality, or spending loads of money (I normally go to the gym until I burn out, barely sleep and constantly do my uni coursework, and either love or scream at people, but that isn't exciting).
I have a hard time calling myself it because I feel like I'm some how faking it, so I just think 'I'm not well' rather than 'I'm bipolar'.