Borderline Personality Disorder Diagnosis: DSM IV Diagnostic Criteria

A pervasive pattern of instability of interpersonal relationships, self image and affects, and marked impulsivity beginning by early adulthood ** and present in a variety of contexts, as indicated by five (or more) of the following:
1) Frantic efforts to avoid real or imagined abandonment.
Note: Do not include suicidal or self-mutilating behavior*** covered in Criterion 5.
2) A pattern of unstable and intense interpersonal relationships characterized by alternating between extremes of idealization and devaluation.
3) Identity disturbance: markedly and persistently unstable self-image or sense of self.
4) Impulsivity in at least two areas that are potentially self-damaging (e.g., spending, sex, substance abuse, reckless driving, binge eating).
Note: Do not include suicidal or self-mutilating behavior*** covered in Criterion 5.
5) Recurrent suicidal behavior, gestures, or threats, or self-mutilating behavior***.
6) Affective [mood] instability.
7) Chronic feelings of emptiness.
8) Inappropriate, intense anger or difficulty controlling anger (e.g., frequent displays of

temper, constant anger, recurrent physical fights).
9) Transient, stress-related paranoid ideation or severe dissociative symptoms.

You need 5 out of 9 to be considered BPD. But it really varies from person to person and usually BPD does not stand alone, you may have other disorders, depression, anxiety etc with it.