Here is my experience. This was my first - and to date, only - suicide attempt from when I was 16.
I texted some friends goodbye - though I'm sure I would have survived regardless due to my method failing, this was how I was found and was the direct cause of the shitshow that ensued in the months following; do not notify anyone unless your goal is to be treated like an infant and prisoner for the next year at least - and took 20g caffeine in conjunction with 32.5g aspirin. No recent use or tolerance to either. I had not eaten in six to eight hours - I forget exactly. I had not slept in 36-40 hours.
I did not take antiemetics, which was my second mistake. I have bulimia - I thought I can simply tell myself not to vomit, just do the opposite of what I usually do. I found out the hard way that body and brain messages are very different. You can resist the former but eventually you will give in. As long as you are in human form it is inevitable. I failed to take this into account. Whereas the latter requires constant motivation and internal push - I forced myself to vomit for my eating disorder, it did not come easily to me. Do not mix up the body and brain signals.
The caffeine dissolved in contact with the most minute amount of moisture - they melted in my sweaty hands - and the taste was quite bitter. Once all 200 pills were swallowed, I sliced my thighs up for fun - shallow cuts, not intending to die from them - just to admire the blood and out of curiosity to spot any difference to usual due to the aspirin thinning my blood. I distinctly recall it looked like paint and that I was impressed with the pattern I drew on myself.
I then attempted to slit my wrists with a pencil sharpener blade. This required more force than I anticipated, and the small, rather dull blade kept getting stuck in my flesh. I was tired mentally and did not have the energy needed to succeed at this - just wanted to take something and fall away into nothingness, not have to put in effort, blah. Eventually, I gave up hope that I would bleed out. A wave of nausea unlike anything I have ever felt before overtook me. Though I tried, I was unable to resist. I partially missed the toilet but no matter. I hoped there were still enough pills in my stomach to do the job. Perhaps at this point there were.
I turned out the light and prepared to die from myocardial infarction. My heart rate was beginning to speed up. If I closed my eyes, flashes of light - akin to a pulsating galaxy - popped into my field of vision. I desperately wanted to lose consciousness and be dead already, but the flashing light and my pounding heart kept me stuck conscious. Yet the heart attack never came. At some point the sweating was no longer on my attention. I forget if I actually stopped sweating or only stopped paying attention to it. I expected to - but did not feel - alert. However, caffeine at normal doses does not affect me the way it does most people; I get only a mild head buzz rather than a true stimulation or sense of awakeness.
I laid down in the fetal position and vomited uncontrollably again shortly thereafter. Lying on the linoleum tiling, I became cold. I haphazardly put on my hat, socks, and clothes (I had been wearing only underthings). The cuts on my wrists stopped bleeding before I fell asleep - they were crusting over when I put my clothes on. I awoke to a bald man shining a flashlight in my eyes and asking me had I taken the entire contents of the empty pill bottles and did I drink anything.
Third lesson - don't wear anything you like. My clothes were ruined with vomit - even if they hadn't been, upon arrival the medics stripped me naked. I never found out where my clothes went - found out later they were tossed in a drawer, became mouldy, and had to be discarded. It's unfortunate. I was quite fond of that hat.
The practical lessons from my story end here - recounting the aftermath will only upset me. You can imagine it well enough yourself if you have any experience with psychiatry or the mental 'health''care' 'profession'. I put all the apostrophes because it is a bloody fucking joke. Pun intended - I self harmed more during 'treatment' than at any other point in my life.
I know that regardless of what others may tell you, you will make your choice. Although I may not agree with it, I respect that it is your choice to make. But I implore you, learn from my mistakes. Do not be like me.