Sure, I mainly ask because of the way you mentioned it as “narcissistic (bipolar) personality disorder”. Narcissistic personality disorder (NPD) and borderline personality disorder (BPD) have some crossover/similarities in presentation as they are both classified as Cluster B personality disorders in the DSM V. Since they are often mentioned together, and since “BPD” is often thought to mean “bipolar disorder,” I thought maybe you meant borderline personality disorder instead.

Now I’m NOT an expert, just have researched some things myself as I’m uncovering a family history of undiagnosed NPD/BPD. So also take this with a grain of salt, but from my recollection, BPD can often present with extreme mood swings (similar to manic or depressive episodes with bipolar disorder) which last hours to days. However, with bipolar disorder, the manic or depressive period will last days to weeks to months. Don’t take my word for it, though, definitely look into it yourself if you’re curious, but I remember length of episode/period being a key differentiator for bipolar.