Bipolar Disorder Support Group
Bipolar disorder is not just a single disorder, but a category of mood disorders marked by periods of abnormally high energy and euphoria, often accompanied by bouts of clinical depression. This is the place to talk about your experience with bipolar disorder, learn from others' experiences, and find support.

I was also diagnosed very late in life after decades of feeling that my previous treatment had not been right but grateful to get a firm answer and then on the meds.
Even if you are expecting a particular diagnosis you go through some psychological grief (as in, how would my life have been different if I'd been different had this been diagnosed earlier) and if you hadn't expected a degree of denial perhaps. Whatever it takes a while to come to an emotional equilibrium with you diagnosis and then acceptance.
Hopefully he's going on meds and that is also likely to be a challenge and can take a while to work out the correct meds for him. Side effects are likely to be an issue, but it is worth it.
Oh and look after yourself, you are likely to go through some emotional turmoil too, but try to be aware of those feelings so they don't impact too much on the support you give him.
Finally, and this might be the hardest part, he's 45 and it's up to him to put the work in and to remain med compliant and wary for when the meds aren't working. Perhaps there will be some lifestyle changes he will need to make too. You can't do that for him.
I'll give you a big hug
This is a treatable illness...Chronic but treatable
There's good treatment to...xo