A drug overdose occurs when a chemical substance (i.e. drug) is ingested in quantities and/or concentrations large enough to overwhelm the homeostasis of a living organism, causing severe illness or death. Essentially is it a type of poisoning.
Drug overdoses are often used to commit suicide. Many drug overdoses are unintentional and are usually the result of either irresponsible behavior (such as overindulging at a college keg party), or the misreading of product labels (such as taking taking 4 pills every 1 hour instead of 1 pill every 4 hours).
A common unintentional overdose in young children involves multi-vitamins containing iron. Iron is component of the hemoglobin molecule in blood, used to transport oxygen to living cells. When taken in small amounts, iron allows the body to replenish hemoglobin, but in large amounts it causes severe pH imbalances in the body. If this overdose is not treated with chelation therapy, it can lead to death.
Common types of drugs that are overdosed on:
The word "overdose" implies that there is a safe dosage and therefore the term overdose is commonly only applied to drugs, not poisons. One can not overdose on cyanide because it is a poison-- it is harmful at any dosage.