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MDCG 2021-24 Guidance on classification of medical devices - October 2021

Medical devices regulation

The classification of medical devices in use by the EU medical device legislation is a risk-based system taking into account the vulnerability of the human body and the potential risks associated with the devices. This approach uses a set of criteria that can be combined in various ways in order to determine classification, e.g. duration of contact with the body, degree of invasiveness, local vs. systemic effect, potential toxicity, the part of the body affected by the use of the device and if the device depends on a source of energy. The criteria can then be applied to a vast range of different medical devices and technologies. These are referred to as the ‘classification rules’ and are set out in Annex VIII of Regulation (EU) 2017/745 on medical devices (MDR). They correspond, to a large extent, to the classification rules established by the International Medical Device Regulators Forum (IMDRF) in the guidance document GHTF/SG1/N77:2012

According to MDR Article 51 devices are divided into the following classes I, IIa, IIb and III, taking into account the intended purpose of the devices and their inherent risks. Classification is to be carried out in accordance with Annex VIII to the MDR. In addition, and according to Article 52(7)(a), (b) and (c), Class I devices can be further subdivided into Is – sterile condition, Im – measuring function and Ir – reusable surgical.

The technical documentation to be drawn up by the manufacturer must include the risk class of the device and the justification for the classification rule(s) applied in accordance with Annex VIII of the MDR. 

This MDCG document offers us a real supporting tool to handle and clarify classification rules of the MDR Annex VIII.  The 22 classification rules are presented as synoptic diagrams to follow to find the good classification (from page 17 of the document). Various examples are also provided.

Rules classification reminder

Duration of use

  • Transient: Normally intended for continuous use for less than 60 minutes.
  • Short term: Normally intended for continuous use for between 60 minutes and 30 days.
  • Long term: Normally intended for continuous use for more than 30 days.

In certain instances the duration of use for a product needs to be considered as the duration of effect. For instance, application of a topical cream to the skin may only take seconds to apply but the cream may remain in situ for many hours. The duration of use should therefore not be considered as the time taken to apply the product but rather the duration for which the product remains in or on the body.

A scalpel may be used on the same patient throughout an operation that may last for several hours. The uninterrupted use for an intended purpose, i.e. cutting tissue, will normally not last for more than a few seconds at a time. Therefore a scalpel is a transient use device. However, where usage of a device is discontinued in order for the device to be replaced immediately by the same or an identical device (e.g. replacement of a ureteric catheter) this shall be considered an extension of the continuous use of the device.


  • Invasive device: Any device which, in whole or in part, penetrates inside the body, either through a body orifice or through the surface of the body. A device that administers energy to the body should not be considered as invasive if only energy it emits penetrates the body and not the device itself.
  • Body orifice: Any natural opening in the body, as well as the external surface of the eyeball, or any permanent artificial opening, such as a stoma.
  • Injured skin or mucous membrane: An area of skin or a mucous membrane presenting a pathological change or change following disease, a wound or a scar.
  • Surgically invasive device: An invasive device which penetrates inside the body through the surface of the body, including through mucous membranes of body orifices with the aid or in the context of a surgical operation; and a device which produces penetration other than through a body orifice.

The term surgical operation used in this definition includes all clinical interventional procedures in which a device is placed into the body through the surface of the body. A surgically invasive device always implies that it enters through an artificially created opening. This can be a large opening, such as a surgical incision, or it can be a pinprick opening made by a needle. Therefore surgical gloves and needles used with syringes are surgically invasive.

Active device means any device, the operation of which depends on a source of energy other than that generated by the human body for that purpose, or by gravity, and which acts by changing the density of or converting that energy. Devices intended to transmit energy, substances or other elements between an active device and the patient, without any significant change, shall not be deemed to be active devices.

Application of the classification rules

Before applying the classification rules, the manufacturer should first determine if the product concerned, based on its specific medical purpose, falls in the scope of the MDR as medical device, accessory for a medical device (Article 2 MDR), medical device part or component for replacement (Article 23(2) MDR) or as a device without an intended medical purpose listed in Annex XVI.

It is the intended and not the accidental use of the device that determines the class of the device.

How to use the rules

The manufacturer must take into consideration all the rules in order to establish the proper classification for its device. The strictest rule and sub-rule resulting in the highest classification determines the class. It is quite conceivable for instance that one of the general rules that is not specific to active devices nevertheless applies to such a device. The intended purpose and all the device characteristics must be taken into consideration. The characteristic or combination of characteristics in accordance with the intended purpose of the device that falls into the highest class determines the class for the device as a whole.

Bonus: the consolidated diagrams offered here:

You can access the diagram from MDCG 2021-24 for non-invasive devices here.

You can access the diagram from MDCG 2021-24 for invasive devices here.

You can access the diagram from MDCG 2021-24 for active devices here.

You can access the diagram from MDCG 2021-24 for special rule devices here.

Our expertise

Since the arrival of Regulation 2017/745, new requirements have been requested and are part of the documentation to be presented to the notified body.

CSDmed brings its expertise and a methodical approach to its customers, manufacturers, importers and distributors of medical devices, thanks to a team of specialized experts and consultants, who will be able to handle the MDR transition in its entirety.

Don’t wait and contact us.