Determining MDR risk classes (I, IIa, IIb, III)

The MDR risk classes are class I, IIa, IIb and III. You determine the class of your medical device using the 22 classification rules in Annex VIII of the EU MDR 2017/745 . The higher the class, the greater the risk to the patient and the more demanding the assessment by a notified body.

The class is the first decision in every MDR process. It determines whether you may affix the CE marking yourself, how much evidence you need and what it costs. Read MDR and ISO 13485 to see how the law and the standard work together, and check the Inspectie Gezondheidszorg en Jeugd (IGJ, Health and Youth Care Inspectorate) for what applies in the Netherlands for market access.

In short: class I is low risk (plaster, wheelchair), IIa low to medium (hearing aid, contact lens), IIb medium to high (ventilator, bone screw) and III high risk (heart valve, hip prosthesis).

What do the MDR risk classes mean?

Each class links a level of risk to a conformity route: the way you demonstrate that your product complies with the law.

Class	Risk	Examples	Notified body needed?
I	Low	Plaster, wheelchair, reading glasses, stethoscope	No, you declare conformity yourself
Is, Im, Ir	Low, with an extra point of attention	Sterile dressing (s), fever thermometer (m), reusable surgical instrument (r)	Yes, but only for sterility, a measuring function or reuse
IIa	Low to medium	Hearing aid, contact lens, short-term urinary catheter, dental filling	Yes
IIb	Medium to high	Ventilator, infusion pump, bone screw, X-ray machine, condom	Yes
III	High	Heart valve, breast implant, hip or knee prosthesis, pacemaker, stent in the coronary artery	Yes, with the most demanding assessment

The examples are typical, not a guarantee. A small change in intended use can move a product up one class.

How do the MDR classification rules work?

Annex VIII contains 22 rules in four groups. You go through all of them. If several apply, the highest class counts.

Rules	Group	Covers
1 to 4	Non-invasive devices	Products that do not enter the body, such as dressings, wheelchairs and blood bags
5 to 8	Invasive devices	Products that enter through a body opening or are inserted surgically, including implants
9 to 13	Active devices	Products with an energy source, including software (rule 11)
14 to 22	Special rules	Medicinal substances in the product, contraception, nanomaterials, animal tissue, disinfection

Three concepts that determine the class

Before you apply the rules, you establish three things. These are set out in chapter I of Annex VIII.

Concept	Meaning	Example
Duration of use	Transient (less than 60 minutes), short-term (60 minutes to 30 days) or long-term (more than 30 days)	A urinary catheter that stays in for 5 days is short-term
Invasiveness	Does the product enter the body, through an opening or surgically?	A contact lens touches the eye, a stent is inserted
Location in the body	Does the product touch the heart, the central circulatory system or the central nervous system?	Contact with the coronary artery often moves a product to class III

The intended use set by the manufacturer is decisive, not what a doctor does with the device in practice. Write that intended use precisely, because it also appears in your technical documentation.

The classification rules in plain language

You do not need to know all 22 rules by heart. This translation covers the rules you will encounter most often.

Rule	In plain language	Outcome
1	Non-invasive and no other rule applies	Class I
4	Contact with damaged skin	I as a mechanical barrier, IIa for most wound care, IIb for deep wounds that heal only from the bottom up
5	Through a body opening (mouth, nose, ear)	Transient I, short-term IIa, long-term IIb
6 and 7	Surgically invasive, transient or short-term	Mostly IIa, class III for direct contact with the heart or central circulatory system
8	Implants and long-term surgically invasive	Mostly IIb, class III for, among others, heart implants, breast implants and joint prostheses
9	Active and supplies or exchanges energy with the body	IIa, IIb if this is potentially dangerous
10	Active for diagnosis and monitoring	IIa, IIb when monitoring vital functions where direct danger can arise
11	Software	See below
14	Contains a medicinal substance with a supporting action	Class III
15	Contraception or protection against STIs	IIb, III if it is implantable or long-term invasive

Rule 11: software as a medical device

Rule 11 placed many software companies one or two classes higher under the MDR than under the old directive. Software that provides information for a decision on diagnosis or treatment is at least IIa.

What could the decision cause?	Class
Death or irreversible deterioration of health	III
Serious deterioration or a surgical intervention	IIb
Other consequences	IIa
Monitoring of physiological processes	IIa, IIb for vital parameters with direct danger
All other software	I

For example, an app that uses a skin photo to indicate whether a mole is suspicious provides information for a diagnosis. A missed melanoma can have serious consequences. Such an app quickly ends up in class IIb or III. An app that only keeps a medication schedule often does not fall under the MDR at all.

Example: determining the class of a wound dressing

A manufacturer makes a silicone wound dressing for pressure ulcers. The wounds extend into the subcutis. The manufacturer works through the rules as follows.

Record the intended use

“Covering and keeping moist pressure ulcers (category 3 and 4) that have broken through the dermis.” This is the sentence everything rests on.

Choose the group

The dressing lies on the wound and does not enter the body. It is therefore non-invasive: rules 1 to 4.

Apply the rule

Rule 4 covers contact with damaged skin. Wounds that have broken through the dermis and can only heal from the bottom up fall under class IIb.

Check the special rules

Is there silver or another medicinal substance in the dressing? Then rule 14 may apply and the class becomes III. In this example, it does not.

Record the outcome

Class IIb, with the justification per rule in the technical documentation.

Had the manufacturer limited the intended use to superficial grazes, it would have been class IIa. The intended use determines the class.

What changes per MDR risk class in your process?

The class determines which annex you follow and how deeply the notified body reviews your product. This has a major effect on the timeline and MDR costs.

Class	Route in brief	Role of ISO 13485
I	Technical documentation, EU declaration of conformity, registration in EUDAMED	Quality system required (Article 10), certificate not needed
IIa	Assessment of the quality system plus a sample of technical documentation per category	An ISO 13485 certificate is the usual basis
IIb	Quality system plus assessment per generic device group, implants per product	As above
III	Quality system plus full assessment per product, usually with clinical investigation	As above, with additional oversight

For everything above class I, you choose a notified body. It also checks whether your classification is correct.

Common mistakes when determining the MDR risk class

Taking the class over from the old directive. Many products, especially software, are classified higher under the MDR. Redo the analysis.
An intended use that is too broad. “For all wounds” pulls your product up to the highest class that applies to any one of those wounds.
Applying only the first matching rule. You must go through all the rules. The highest outcome applies.
Forgetting accessories. An accessory gets its own class, separate from the main product.
No justification. An auditor wants to see per rule why it does or does not apply.

Torn between two classes? Discuss it with your notified body or with the competent authority. In a dispute between the manufacturer and the notified body, the competent authority decides (Article 51 MDR).

Help with classification under the MDR

The Medical Device Coordination Group (MDCG) has an extensive guidance document with examples per rule: MDCG 2021-24 on classification. You can find it via the guidance page of the European Commission . For software, MDCG 2019-11 is the standard source.