here is her response from the bipolar group:

You can have both, I do and there's only one difference regarding medication, BPD folk can be on an anti-depressant alone (if the dominant mood is depression) while no way in hell you can do that to BP person because it will cause hypo/mania.

So yes it does matter which diagnosis is accurate not only because of meds, but also because DBT is highly recommended for BPD, as meds cannot fix the screwed up thought distortions.

For me there are a few main differences that stand out which helps me identify what exactly I'm dealing with on any given day.

BPD:
Moods are reactionary, usually something or I should rather say someone triggers a mood swing. The only time its not directly triggered by an event, its triggered by feelings of emptiness and hopelessness, who's roots I will find in my skewed view of my relationship or irrational fear of losing my relationship.

If I am in a BPD mood, external factors can affect it and swing me in the opposite direction too. Example, I'm depressed and wanting to self-harm because my bf is out of town and I miss him. Should bf have a bunch of roses delivered to my house, GOOD BYE depression I am on top of the world!
Also my BPD moods swings are much more short lived than my BP swings.

BPD is largely driven by distorted thought perceptions and an insane fear of abandonment, whether there is a real threat of being abandoned or not. That's why DBT comes highly recommended because it helps to manage those thought patterns and thus decrease the amount of damage we cause to our loved ones by "acting out" (gosh I hate that term but I'll be the first to admit I have the emotional IQ of a child) which in turn helps to minimise the turmoil we experience so frequently.

My BP

My moods are 99% random, the 1% being stress induced. I will wake up in the morning highly upset and depressed by the fact that I'm breathing and I will probably stay that way for minimum a week. Likewise, I can and have woken up at 3am feeling insanely happy, energetic, motivated and inspired to do a load of washing.

These 2 opposite moods are also accompanied by huge shifts in energy. When I'm depro, my body feels like its made of concrete and I struggle to just get out of bed, when I'm hypo I'm like fricken tigger, bouncing off the walls, can't sit still for shyt, and sleep is for the dead.

Also, my BP swings cannot be influenced by external factors. A bunch of roses will not a depressive episode end. I doubt I would even smell them or think how pretty they are or how thoughtful my bf was. They will have zero impact on me, so I have to surf out each wave because they always come and go just as they please.

Uhm.. I think I've covered the basics as I see them from my POV. Hopefully I didn't forget anything fundamental, but if I did I'm sure another poster will add it.

Hope this helps!