Bipolar disorder typically develops during the adolescent or young adult years. One phase of bipolar disorder is an episode of illness called as "hypomania." During this phase there is a period of abnormally increased energy and productivity that -- unlike mania -- doesn't involve psychosis and doesn't interfere with someone's ability to function. Left untreated, however, hypomania can occasionally progress to severe mania and, more often, to episodes of depression.
A full manic episode is diagnosed if an elevated mood occurs with three or more of the symptoms related to sleep, energy, thinking, and behavior most of the day, nearly every day, for at least one week, and the symptoms interfere with someone's ability to function. If irritability is present, then four or more symptoms are required for diagnosis.
A depressive episode is said to exist if five or more depressive symptoms exist for most of the day, every day, for two weeks or more.
A psychiatrist is usually the type of doctor who makes the determination of bipolar disorder. Frequently blood and urine tests are done to rule out drug use as the cause of symptoms, or certain illnesses such as thyroid disorder.