Article from International Overdose Awareness Day
From the article:
"An overdose means having more of a drug (or combination of drugs) than your body can cope with. There are a number of signs and symptoms that show someone has overdosed, and these differ with the type of drug used. All drugs can cause an overdose, including prescription medication prescribed by a doctor. It is important to know the right amount and the right time to take your medication. It is also vital to know what drugs should not be mixed, and to seek help if you feel you are not in control of your drug use."
This article provides basic information on different types of overdoses, and has fact sheets on various drugs.