There is a lot of confusion these days when the term Bipolar Disorder is used. Historically Bipolar Disorder referred to one of the most serious psychiatric disorders and a relatively rare condition called "Manic Depressive". A normal 'mania' of the manic depressive disorder could last up to four months and lead to death from exhaustion and over activity. As one person who developed mania later said, it was "like being on constant cocaine without the cost of the drug." During frank mania the person is grandiose, experiences surreal highs, is delusional with hallucinations. They literally talk to God and can be extremely violent. The depression of Manic Depression was the most likely to be associated with suicide so was very dangerous. The Manic Depressive disorder was a hospital based disorder.
Today Bipolar Disorder refers to the idea that all mood disorders are part of a spectrum. Bipolar II refers to a person who has days of irritability and mood swings so that in fact Bipolar Spectrum Disorders may be any variation of mood from a steady state of euthymia or 'feeling okay'.
At the same time the whole idea of mood "disorder" must be considered in the context that Bereavement or Grief that persists longer than 6 weeks is considered pathological despite the fact that parents routinely say they never get over the depression of losing a child.
Today Bipolar Disorder can refer to the worst and the least of psychiatric conditions. Where once it was 'necessary' for a person with Bipolar disorder to be hospitalized and treated with medication there is no need for hospitalization or pharmaceutical treatment of the Bipolar Spectrum Disorders. In deed, it's been found that aerobic exercise can be equivalent to prozac in the treatment of depression and psychodynamic psychotherapy has long been shown to be equal if not better in the treatment of depressive disorders which are now subsumed by the Bipolar Spectrum Disorder definition. Further if medication is considered a wide range of medications can be used including the traditional antidepressants which explains why today it's more common to see medications used in common that once were considered 'uppers' or 'downers', the idea being that the medication is modulating the illness rather than changing it from one 'state' to another'. That said the vast majority of bipolar disorders today are not treated with hospitalizations and epidemiologically most who might fulfill the diagnosis of having a Bipolar Spectrum Disorder will not be on medications. There are indeed some who argue that the antidepressant medications in some cases caused bipolar disorder though most would not accept this.