Cyanide isn’t going to kill you instantly, but if it is the right dosage, it’s going to kill you pretty quick.
Cyanide pills aren’t made, at least in any way accessible to a the average person. You can’t even buy cyanide itself unless you are a lab or a manufacturer. It is frowned upon to be able to by extremely lethal poison that can kill people quick and easy.
You would have to make your own, and something tells me you aren’t much of a chemist.
I don’t know you or what you are going through, but I do know there are resources out there. Give yourself a cool off period before you make the most permanent decision of your life.
I won’t do the whole “people care about you, it gets better, there is so much to live for” thing, because it’s a stupid bullshit line people say. People have the agency to choose whether they want to live or not.
What I can say is that when I’ve been suicidal in the past, I always give myself 72 hours before making that final decision. So far, something in that 72 hours has kept me here, even if I was angry and miserable about it.
Death isn’t relief; it is the absence of anything, including relief. You’ve got to be alive to feel relief from what you are feeling. Taking cyanide or something else is total annihilation of being able to feel anything.
If you are dead set on suicide, you’ll be dead soon anyways, so why not keep on fighting a little bit longer as a big fuck you to who or what is making life shitty?