Please be gentle as this relates to a situation I'm in that is very raw.
If you had a friend who was going through something devastating, like cancer treatment, you'd of course understand that for at least the length of the chemo (if not longer) you're going to need to be selfless i.e. not put any of your problems on your friend, simply be there for them, check in with them as often as possible (if they want that), try and do thoughtful things for them, drop everything and go away with them for a weekend at their request etc.
But, once treatment is done and you're half a year down the line, how long is it reasonable to accept the friendship being completely one-sided to the point you're getting literally zero back, i.e. they're not even asking "how are you?" when they see you, just talking about their own lives? Especially if you have your own ongoing debilitating health condition (one that can also sometimes result in death), mental health difficulties, family issues, deaths in the family etc that you are simultaneously dealing with.
I feel completely unreasonable even asking this question but I also am in a brain loop over it and need a bit of outside perspective.