In order to get Social Security Disability your Bi-polarism has to hinder you ability to work. If you cannot work because of this you may be able to get a monthly disability check from Social Security.
Unless your disorder is not able to be properly treated with medication, then SSI would not be your primary remedy. See a doctor for medication efforts before enrolling in SSI.
Bipolar mood disorder does count as a mental illness for which one can classify as disabled for the intent of collection Social Security Income. Once classified as disabled, however, it may be difficult to get employment later. This can make you eligible for Medicaid but disqualify you for private medical insurance.