Depending on your tolerance levels. Everyone is different. I would never ever consider killing myself with tablets of any kind, some people succeed, some people dont...some people end up in a psychiatric ward, others end up with irreversible brain damage. You could become a vegetable relying on people to feed you, toilet you...how humiating.
My suggestion to you if you really feel so bad that you want to kill yourself talk to someone now, ring up a friend, you need support right this very moment. When this crisis is passed, you will need some counselling because no one decides to take their life for no reason...so whatever has happened to you to make you feel like this has a solution. But if you are dead, or end up with brain damage, you wont be able to get to that solution. You dont know what is around the corner....something wonderful is awaiting you...I guarantee it. Do whatever you have to do to keep yourself alive and in time you will look back on this part of your life when you are happily married to the man/woman of your dreams and you will thank God you didnt succeed in killing yourself or sustain severe brain damage. Good things will happen to you, but you have to be healthy for that to happen. Go get help now.
You are a child of the universe, no less than the trees and the stars, you have a right to be here, and whether or not it is clear to you, the Universe is unfolding as it should. These are very comforting words from the "Desiderata" ....go find a copy and read it.