Toxicology is the scientific study of adverse effects that occur in living organisms due to chemicals. It involves observing and reporting symptoms, mechanisms, detection and treatments of toxic substances, in particular relation to the poisoning of humans.

It includes environmental agents and chemical compounds found in nature, as well as pharmaceutical compounds that are synthesized for medical use by humans. These substances may produce toxic effects in living organisms including disturbance in growth patterns, discomfort, disease and death.

Forensic toxicology is a discipline of forensic science concerned with the study of toxic substances or poisons, of which there are many thousands. Toxicology encompasses theoretical considerations, methods and procedures from many disciplines including analytical chemistry, biochemistry, epidemiology, pharmacodynamics, pathology, and physiology.

Currently, forensic toxicology is the study of alcohol, drugs (licit and illicit) and poisons, including their chemical composition, preparations and identification. It includes knowledge about the absorption, distribution and elimination characteristics of such substances in the body, as well as the manner in which the body reponds to their presence and the factors which determine drug safety and effectiveness. To understand drug action one must know where and how the effects occur in the body.