A medical device is an object which is useful for diagnostic or therapeutic purposes. Examples of medical devices include medical thermometers, blood sugar meters, and X-ray machines.

European definition

Directive 2007/47/ec of the European Parliament and of the council of 5 September, 2007, which amended the Council Directive 93/42/EEC of 14 June, 1993 concerning medical devices, defines a medical device as any instrument, apparatus, appliance, software, material or other article, whether used alone or in combination, including the software intended by its manufacturer to be used specifically for diagnostic and/or therapeutic purposes and necessary for its proper application, intended by the manufacturer to be used for human beings. Devices are to be used for the purpose of:

• Diagnosis, prevention, monitoring, treatment or alleviation of disease.
• Diagnosis, monitoring, treatment, alleviation of or compensation for an injury or handicap.
• Investigation, replacement or modification of the anatomy or of a physiological process
• Control of conception

This includes devices that do not achieve its principal intended action in or on the human body by pharmacological, immunological or metabolic means, but which may be assisted in its function by such means.

The Medicines and Healthcare products Regulatory Agency (MHRA) regulates medical devices in the UK under European legislation. Medical devices must not be mistaken with medicinal products.

Definition in USA by the Food and Drug Administration

A medical device, according to the U.S. Food and Drug Administration (FDA), is an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is:

• recognized in the official National Formulary, or the United States Pharmacopoeia, or any supplement to them,
• intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or
• intended to affect the structure or any function of the body of man or other animals, and which does not achieve any of its bnvbnbvprimary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes.

as defined by the Federal Food, Drug, and Cosmetic Act, 21 United States Code 1 (h).

Definition in Canada by the Food and Drugs Act

The term medical devices, as defined in the Food and Drugs Act, covers a wide range of health or medical instruments used in the treatment, mitigation, diagnosis or prevention of a disease or abnormal physical condition. Health Canada reviews medical devices to assess their safety, effectiveness and quality before being authorized for sale in Canada.