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Toxicity studies can be divided into laboratory studies using live animals (in vivo studies) or groups of cells (in vitro studies), and studies of human populations (epidemiological studies). Animal studies are used to test chemicals for their acute and chronic toxicity by various routes of exposure. The standard way of measuring a chemical's acute toxicity is to feed it at a range of single doses to groups of laboratory animals, such as rats. The dose that kills 50% of the group, the LD₅₀ (lethal dose-50), is then recorded as well as the effects noticed in the animals. One use of LD₅₀ values is in deciding how to label chemicals under the Chemicals (Hazard Information and Packaging for Supply) (CHIP) Regulations.

The dictionary of substances and their effects volume 1, The Royal Society of Chemistry, 1992

Table 5 lists various measures of the acute toxicity of MEK, and illustrates some of the differences that are used in these tests. Table 5 lists four routes of exposure, oral, skin, inhalation and intraperitoneal injection, and four of the most commonly used laboratory species. Inhalation toxicity is described as a lethal concentration-50 (LC₅₀) rather than LD₅₀, and concentrations are expressed as milligrams or grams of substance per m³ of air, or in parts per million (ppm). The LC₅₀ is only meaningful if the duration of exposure is known. The other doses are expressed as milligrams (mg) or grams (g) of substance per kilogram (kg) of body weight.

A chemical's irritancy is tested by applying it to the eyes and skin of animals. One such test is known as the Draize test, which involves applying chemicals to rabbits' skin and eyes, rabbits being chosen because of their large and exposed eyeballs. The Draize test has frequently been criticised by animal rights campaigners, particularly when used to assess the irritancy of cosmetic products.

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