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From D it's already a liquid. I hope you ordered at least 2 bottles. You can drink it directly or mixed with a bit of water. Be careful because it knocks you out in a few minutes. So don't over mix it, otherwise you'll pass out before you can finish the dose.
One bottle will probably kill you. I think one of the organizations Dignitas or whatever noticed that with a small percentage of people there was prolonged coma for a few hours before death when only one bottle was used. So they switched to using two bottles.