How common is it to be diagnosed with bpd but actally be bipolar?

And the other way!: Bipolar is a mood disorder - supposedly factual. Bpd is a personality style that makes it difficult to function well - some question if pds should even be diagnoses but rather descriptions or opinions. If one also has objective extreme moods that last long enough, they'll have a dual dx. This is certainly a frequent combo. But it probably is possible not to be both.