Are you ok?
"Hi, how are you?" - the standard hello in which the asker has no real desire to understand how the person they're asking is actually feeling, other than to respond, "ye ok thanks, you?" similarly, with no expectation of a response containing anything that resembles feelings.
The slightly more searching "How are you doing?" seems to probe a little further and it's certainly a step above the immortal "How are things?" which dismisses the person and makes the subject the "things" in the persons life, not the person themselves.
This is by no means a critique of the person using these terms, I use them myself more times a day than I could count, but when we really care, when we really want to check in on someone's wellbeing, we need to ask twice.
A: How are you?
B: Good thanks, you?
A: How are you really?
That is until you get that special type of relationship, when asking just once, in the right way and at the right time, is enough.
Those are the relationships to hold on to as if life depends upon it because really, it just might.