Never underestimate the power of denial!
Many times people do not want the stigma, so they just deny everything.
Only a trained professional can diagnose bi-polar (typically it takes multiple sessions because bi-polar is often confused with quite a few other diagnosis')....with that being said...having manic episodes definately rules out a number of things, though I'd be interested to see a 'tox report because many times manic-like symptoms can be due to covert substance abuse.
I'll leave the meds explanation up to a prof.
-pedagogue