Might somebody have bipolar without other people knowing?

Other people?: Depending on many things, other people can miss lots of things about those around them. But that's about them. Your efforts to hide may or may not be effective at deceiving others, but you'd know and that's most important. Try to find help in really dealing with this painful and serious condition - or it may be a mild case . A good psychotherapist can really help &, if needed, medications can too.

That might occur: depending on where the person is on the bipolar spectrum. It is usually hard to miss full blown mania. But hypomania or depression might not be so obvious to others.