The disturbances suffered by those with borderline personality disorder have a wide-ranging and pervasive negative impact on many or all of the psychosocial facets of life, including ability to hold down a job and relationships in work, home, and social settings. Comorbidity is common; borderline personality disorder frequently occurring with substance use disorders and mood disorders. Attempted suicide and completed suicide are possible outcomes without proper care and effective therapy.

Diagnosis is based on the self-reported experiences of the patient, as well as markers for the disorder observed by a psychiatrist, psychologist, or other qualified diagnostician through clinical assessment. This profile may be supported and/or corroborated by long term patterns of behavior as reported by family members, friends or co-workers. The list of criteria that must be met for diagnosis is outlined in the DSM-IV-TR.^[2]

An initial assessment generally includes a comprehensive personal and family history, and may also include a physical examination by a physician. Although there are no physiological tests that confirm borderline personality disorder, medical tests may be employed to exclude any co-occurring medical conditions that may present with psychiatric symptoms. These include blood tests measuring TSH to exclude hypo- or hyperthyroidism, basic electrolytes and serum calcium to rule out a metabolic disturbance, full blood count including ESR to rule out a systemic infection or chronic disease, and serology to exclude syphilis or HIV infection; two commonly ordered investigations are EEG to exclude epilepsy, and a CT scan of the head to exclude brain lesions.