yeah agree with the guy above, ketamine would help with another form of suicide but not cutting. You would still somehow feel the pain. Also honestly it depends how strong the ket you have is so its hard to say. But if you're going to take it honestly I wouldn't overthink it. Probs between 1 and 3 average sized lines depending on the strength. Take one, wait a bit, see how you feel, if you feel like another take another...its, not a big deal. I used to take ket all the time at one stage...never thought about it, just make a line and snorted it... I didn't have to take out a fucking ruler or something, and here I am to tell the tale