Hi @BlueBay
It can be very hard to determine between the two as there can be a lot of crossover, along with the possibility of having both. I read somewhere the other day that about 15% of people with BPD also suffer from bipolar, along with even higher chances of having other types of mental illness (they called them co-morbidities). I'll try to find the link.
Here it is, from the National Education Aliance Borderline Personality Disorder website.
I've been diagnosed as bipolar I, but found I tick a lot of boxes for BPD as well. Could I have both? Sure, but right now things aren't to bad for me so I'll settle for just the bipolar at the moment.
There are 'tests' you can do online & with both illnesses I seem to score high. The Black Dog Institute has some great information on bipolar along with a screening test for bipolar. With a score of 22 or more reportedly (when combined with depression) it has an 80% chance of detecting bipolar. I manage to more than double that. Whenever I do a BPD test I usually get around the higher levels.
I guess the big thing when thinking about bipolar is the highs. I have manic episodes so it's easy to see when I'm well above any normal level of just feeling good. With bipolar II you don't get to that level so at times it can be hard to realise you are over the top.
You say when you go out with friends you sometimes feel high for a while, but is this just a normal thing associated with being out, relaxing with friends or is it more? Does it happen at other times? You have no control when hypomania strikes, so if you only feel this way in certain situations there has to be some doubt. And it's hard to gauge how high you really are in a social setting unless it starts going to the extremes.
I guess we have to leave it to the professionals to work it out for us. I'm glad your psych decided you need more assessment rather than just doing it all in an hour. Sounds like they want to get it right. Because of the impact any diagnosis can have on your life it is so important to get it correct. Hope you can get it sorted soon.
Take care, stay safe.