Your friend might ask if they can talk to you in person. If you can't meet with them, give them a call. A Skype call, FaceTime, WhatsApp video call, even, but, make sure you speak with them. Maybe that said friend just wants to hear your voice and so, actually, a chat on the phone will suffice. NEVER be 'too busy' to set aside all of 5 minutes for someone you call "a friend". If you really cannot spend time with them, or on a phone call, send a recorded voice message. There's always a way in which you can be there for someone. To ignore their message, or fob them off should not be an option!
Do whatever you can do, within reason, to reassure your FRIEND that you want to be there for them and will make every effort to do so.
Several years ago a beautiful, sweet, genuine friend of mine (who was like a sister to me) committed suicide. She was 16. On the day that she took her life I had promised to call her. I was unable to honour my promise because, at the time I was living at the family home and was not allowed to use the house phone. I could've easily gone out to top up my (then pay as you go) phone but, I chose not to.
I know now that her death is not my fault, nor the fault of anyone else. I know that her woes had been with her long before she and I met but,her suicide; her choice to take her own life, affected me in ways I cannot put into words because, for the absolute longest time, I did in fact blame myself. I firmly believed that my call would've saved her.... To this day, although I no longer feel guilty, I still feel so awful about the circumstances. Why wasn't the call important enough; why wasn't she important enough for me to go out and top up my mobile?
She and I spoke in detail about her troubles. Until that horrid day, I was the readily available shoulders to cry on, gave all the cuddles she wanted and the distractions through music and banter that she craved. I'll never forget the call I received from her mother to inform me that my dear, darling, friend, whom I had grown so fond of, had hung herself in her bedroom on the day I was due to call.
Sherelle Black was one of the shiniest humans I'd ever met and those who knew her will know exactly what I mean by that. A generous heart and such a lovely disposition, she made my time on the Theatre summer project where we met the absolute best and I miss her. I will always miss her.
You don't know what anyone is truly dealing with (deep down); how desperate they may feel about certain aspects of their life but, hearing from, or seeing you could potentially have a positive impact on them. It might just stop them from making a decision that will haunt you forever! I AM NOT SAYING SHOULD IT BE THE OPPOSITE THAT YOU WILL BE TO BLAME, absolutely not!! I am saying, wherever possible, MAKE AN EFFORT WITH THE ONES YOU CLAIM TO LOVE AND CARE ABOUT.
There have been times when I've asked / invited certain 'friends' to meet with me and haven't received a reply, or I've been asked, "why, what for?". I don't give them an answer. In fact, I don't contact them again. A true friend, in my opinion, will simply reply with, "sure, when were you thinking?" Or, "I can't meet with you at the moment but, I can give you a call sometime soon. Let me know when is good for you?". No matter what you might be going through yourself, please try not to reject someone who reaches out to you.
We all need someone. Nobody wants to be out here with life's hardships alone. Also, the one in need will not necessarily reach out directly stating their reason for doing so. They may share their work with you, or something funny just to grab your attention and engage you in a conversation in which they can ease their way into opening up about their troubles. Sometimes, there's nothing gravely wrong until your rejection...
So, again, when a friend reaches out to you, send back a positive response. Look out for your friends the very same way you expect, or would like them to look out for you. If you don't consider them a friend of yours, tell them. Quit stringing them along!