Could overdosing on drugs kill you?

Yes: Overdosing on some medications and illicit drugs can be lethal.

Depends: Many drugs, but not all, have a toxicity level which can disturb some bodily function enough to cause death. For most this is a serious amount of drug, unlikely to be had on hand. For many painkillers and drugs of abuse, this is a real possibility. Try your best to know what you are taking and never take an unknown drug in non-medical situations like raves.