Medical Devices Classification

This section describes how ‘general’ medical devices (i.e. those that fall within the scope of the Medical Devices Directive) are categorised into classes according to the degree of risk inherent in the device.

Abbreviations used
MDD – Medical Devices Directive (93/42/EEC)
AIMDD – Active Implantable Medical Devices Directive (90/385/EEC)
IVDMDD  – In Vitro Diagnostic Medical Devices Directive (98/79/EC)

The directives are available on the European Commission website (external link)

The MDD covers a vast range of products from first-aid bandages and walking frames to CT scanners and non-active implants. Given this wide range, it is not justifiable to subject all devices to the same levels of conformity assessment. It is important, therefore, that the level of control is matched, as far as possible, to the degree of risk inherent in the device.
Attempts were therefore made to set the controls relative to the perceived risk in an effort to make them as relaxed as possible (to ease the bureaucratic and financial burdens on business) and as strict as necessary (to ensure that the health of the patient and user is adequately protected).
The classification of devices is therefore a risk-based system. The criteria for classification are described in Annex IX of the MDD.

The classes
‘General’ medical devices are grouped into four classes as follows:
Class I - generally regarded as low risk
Class IIa - generally regarded as medium risk
Class IIb - generally regarded as medium risk
Class III - generally regarded as high risk

Classification of a medical device will depend upon a series of factors, including:

  • how long the device is intended to be in continuous use
  • whether or not the device is invasive or surgically invasive, 
  • whether the device is implantable or active
  • whether or not the device contains a substance, which in its own right is considered to be a medicinal substance and has action ancillary to that of the device.

The difference between each class rests in the choice of conformity assessment procedures available. The section 'Conformity assessment and the CE mark' has a description of the various conformity assessment routes available to manufacturers.
It is the stated intended purpose of the device, assigned by the manufacturer, which determines the class in which a device is categorised.
Since the publication of the MDD there have been specific directives amending the classification of breast implants (2003/12/EC) and total joint replacement implants (2005/50/EC) to class III. In addition, a number of changes that affect classification are included in Directive 2007/47/EC (see European Commission website external link).

The Medical Devices (Amendment) Regulations 2007 No 400 (external link)

MHRA guidance on the Commission Directive 2005/50/EC on the reclassification of total hip, knee and shoulder joint replacementsPDF file (opens in new window) (53Kb)


  • The IVDMDD (98/79/EC) classifies IVDs into four risk categories (see section on In Vitro Diagnostic Medical Devices for further details).
  • Active implantable medical devices are regarded, by their very nature, to be classed as high risk devices in terms of the AIMDD (90/385/EEC).
  • Accessories to a medical device are classified in their own right, separately from the device.

The European Commission has also produced very detailed guidance ‘Classification of medical devices’ MEDDEV 2.4/1(external link).

Disagreements on classification
It is for the manufacturer to initially determine the classification of their product(s). This will allow them to select a notified body (if required) with the ability to carry out the appropriate conformity assessment procedure. It will then be for that notified body to confirm the classification arrived at by the manufacturer before embarking upon the process of conformity assessment.
In the event that the manufacturer and the notified body cannot agree on the classification, either party can refer the matter for a decision to the competent authority that designated the notified body. If doubt still exists, the European Commission, acting in conjunction with a regulatory committee composed of experts from the member states may be approached for a ruling. Similarly, the European Commission, in conjunction with the regulatory committee, may adapt the rules if experience shows this to be necessary.

The layout of Annex IX
The Annex opens with a series of definitions (invasive, active, duration such as long-term etc) so as to minimise any possible ambiguities. There follows a series of implementing rules which lay down the basic principles, such as ‘If more than one rule applies to a device, the highest classification stands’. It should be noted that the definition of a medical device has recently been amended to bring within its scope ‘standalone software’.

The aims of the rules
The rules are a set of broad statements relating to situations, functions, parts of the body treated, properties etc, rather than a list of products which would require constant updating. This has the merit of being more flexible and better able to accommodate new developments in medical technology.
There are four groups within the rules as follows:

  • Rules 1-4 - non-invasive devices
  • Rules 5-8 - invasive devices
  • Rules 9-12 - additional rules applicable to active devices
  • Rules 13-18 - miscellaneous rules for products which merit a higher classification than they might otherwise be assigned

Reclassification of some medical devices by the revision Directive 2007/47/EC (which came into force in March 2010):

  • the definition of the central circulatory system has been amended to include arcus aorta and aorta descendens which will reclassify some devices to Class III
  • under Rule 6 devices in contact with the central nervous system are now Class III
  • under Rule 15 devices intended for disinfecting invasive devices are now Class IIb (was IIa)
  • under Rule 16 all devices intended for recording X-Ray images are now Class IIa (was non-active only).

Page last modified: 16 August 2013