“That sounds genuinely awful. I'm not surprised you reacted like that.”
Instead of: I'm sure they didn't mean it — try not to take it personally.
Different from family or a partner
If a friend has BPD
Friendship has a different licence from a partner or a parent. Less obligation, less history, and — usefully — less at stake in every conversation. That combination makes a friend one of the more effective people in someone's life, provided the limits are clear.
What a friendship is and is not good for
Being clear about this is what keeps the friendship rather than what ends it.
Good for
Ordinary contact
The single most useful thing you can offer. Unremarkable, regular, low-stakes contact is what stops one relationship becoming someone's entire emotional infrastructure — and it costs almost nothing.
Good for
Being a second opinion
You are outside the intensity. 'That sounds like it hurt, and I don't think he meant it that way' is available to you in a way it is not to a partner.
Not for
Crisis management
You are not a service, you are not trained, and you cannot assess risk. Knowing the crisis lines and being willing to say 'I think you need to call them, and I'll stay on the phone while you do' is the right version of helping here.
Not for
Being the only one
If you have become the person they contact about everything, that is a load a friendship cannot hold, and saying so early is much kinder than withdrawing later.
Things worth being able to say
Each replaces something that is either dishonest or unsustainable.
“I can't do tonight. I can do a call tomorrow evening.”
Instead of: [No reply for two days]
“I'm not the right person for this bit. Have you got someone you can talk to who's trained?”
Instead of: [Staying up until 3am, out of your depth, every week]
“I've noticed I'm the person you call for everything, and I don't think I can be that.”
Instead of: [Quietly replying less until the friendship fades]
“I'm still here. I'm just not available right this second.”
Instead of: Sorry, been busy!
“If you're not safe, I want you to call someone who can actually help. I'll stay with you while you do it.”
Instead of: Please don't do anything, promise me.
The situations that come up
Including the two that make people quietly withdraw.
What if they've split on me?
Say very little, do not argue the case, and stay reachable. Splits usually pass in hours to a couple of days. What ends friendships here is not the split — it is responding to it as though it were a settled verdict.
What if they only contact me in crisis?
Then the friendship has become a service, and that is worth naming kindly and early. Suggesting ordinary contact — a walk, a coffee, something with no agenda — often changes the pattern more effectively than any conversation about it.
Should I mention I think they might have BPD?
Generally no. Naming a diagnosis at someone rarely lands as care. Describing behaviour and its effect on you, specifically and without a label, is the version that occasionally helps.
What if I can't cope with it?
Then reduce contact honestly rather than disappearing. A stated, smaller version of the friendship is much better for both of you than a silent fade, which will be experienced as exactly the thing they are most afraid of.
What if they're in danger?
Crisis lines, emergency services, or their named support if you know it. You are not equipped to hold this and it is not a failure to say so. Staying on the phone while they call someone is often the most useful thing you can do.
Is there anything I should read?
The mechanism chapters of a book like this one make an enormous difference to how you interpret what you are seeing. The skills chapters are written for them rather than for you.
Educational disclaimer: this page supports book discovery and general learning about borderline personality disorder. It does not diagnose, replace individualised professional care, or provide emergency support. If you are in crisis, contact local emergency services or a crisis line — see the crisis support page.