From the NIMH:
Bipolar disorder, also known as manic-depressive illness, is a brain disorder that causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks. Symptoms of bipolar disorder are severe. They are different from the normal ups and downs that everyone goes through from time to time. Bipolar disorder symptoms can result in damaged relationships, poor job or school performance, and even suicide. But bipolar disorder can be treated, and people with this illness can lead full and productive lives.
MANIA: Irritability, Feeling “high”, Talking very fast, Easily distracted, Sleeping very little
DEPRESSION: Feeling sad or hopeless, loss of interest, feeling tired, Changing eating and sleeping habits
A quiz to help you see if you have symptoms of bipolar disorder: http://psychcentral.com/quizzes/bipolarquiz.htm
This is NOT a diagnosis and if you feel the symptoms, go see your doctor.