Hi @kato and thanks for posting such a great question.
Yes – Sometimes, people can live with two (or more) diagnoses that co-occur at the same time. In some circumstances, a person’s original diagnosis may be reassessed, and an updated diagnosis can be given.
In your situation, it sounds like you have just started seeing a new psychiatrist who is still getting to know you? They have tentatively suggested BPD, but this is not yet official - is that right?
There can be a certain amount of symptom overlap between different diagnoses. For this reason, sometimes clinicians may deliberate for a period of time, as they get to know you. Bipolar and BPD do have some similar features (e.g., impulsivity, fluctuations in mood), however they are categorised as distinct disorders in the DSM-5 (that’s the big, fat book that clinicians refer to when making a diagnosis).
Every individual is amazingly unique and beautifully different… and for this reason an accurate diagnosis can sometimes take some time. This can be frustrating for some people, but it's important to let our treating mental health professionals to take the time they need to ensure they're 'getting it right'.
If a person does receive a new or additional diagnosis, people can still of course receive treatment. What exactly this treatment would look like could vary considerably, and would vary according to the needs of the individual.
SIGH… Wouldn’t it be easier if mental illness was just like when we break our leg, we could just go and get an x-ray?! Put on a cast, let it heal, and then be on our merry way! But then again, I kind of think the mystery behind the human brain is one of the reasons why I love psychology as much as I do 🙂
@kato have you discussed with your psychiatrist the concerns you have about potentially receiving a change to your diagnosis? It is important you feel informed, so remember to ask lots of questions if you need to.