EU MDR Classification Rules: The 22 Annex VIII Rules That Set a Device’s Class

The EU Medical Device Regulation (Regulation (EU) 2017/745, replacing Directive 93/42/EEC and fully applicable since 26 May 2021) does not classify a device by looking up its product category in a table. It classifies by running the device through a fixed set of 22 rules in Annex VIII, each keyed to physical characteristics — invasiveness, duration of contact with the body, whether the device is active, and a handful of special categories that do not fit those three. The rule (or rules) that apply determine which of four risk classes the device lands in, and that class determines everything downstream: which conformity-assessment route applies, whether a Notified Body is involved at all, and how much clinical evidence a technical file needs to carry.

This page walks the rule structure itself — not a single device class in isolation, and not the post-classification requirements (those are covered on CASRAI’s Class IIa medical device guide). It is the step that has to happen before either of those is relevant.

The four classes, in outline

MDR sorts devices into four classes of ascending risk. Class I is the only class that generally does not require Notified Body involvement, and even within Class I there are three sub-categories that do:

• Class I — low risk, self-declared by the manufacturer in most cases. Typical examples: non-sterile bandages, hospital beds, examination lamps (Class I devices can be active). Three sub-categories still require Notified Body review of that specific aspect: Class Ir (reusable surgical instruments, e.g. forceps), Class Is (devices placed on the market sterile, e.g. sterile syringes), and Class Im (devices with a measuring function, e.g. clinical thermometers).
• Class IIa — medium risk, Notified Body conformity assessment required. Typical examples: short-term corrective contact lenses, feeding pumps, polymer-film wound dressings.
• Class IIb — higher risk, more extensive Notified Body scrutiny and clinical-evidence requirements. Typical examples: long-term contact lenses, urinary catheters, lung ventilators, radiation-emitting devices such as therapeutic X-ray sources.
• Class III — highest risk, the strictest requirements MDR has. Typical examples: heart valves, pacemakers, drug-eluting stents — life-sustaining or life-supporting implants, and devices incorporating a medicinal substance as an integral part.

See CASRAI’s What Is a Medical Device? guide for the underlying legal definition that determines whether a product is a device at all before classification is even a question, and the IVD-specific track if the product is an in vitro diagnostic — IVDs are classified under a separate rule set in the sister regulation, IVDR 2017/746 (Classes A–D), covered in CASRAI’s IVDR requirements guide. The two rule sets are not interchangeable, and applying MDR’s Annex VIII rules to a diagnostic is a real, recurring sourcing mistake.

The four rule groups

Annex VIII’s 22 rules are organised into four groups by device category, and a device is classified under the group it actually belongs to — not every rule applies to every device:

Rules	Category	What they classify
Rules 1–4	Non-invasive devices	Devices that do not enter the body through a body orifice or the skin — classification here turns mainly on whether the device channels or stores substances for later infusion/administration, and whether it can affect the biological or chemical composition of blood, other body fluids, or transplanted organs/tissues/cells.
Rules 5–8	Invasive devices	Devices that penetrate the body, wholly or partly, through a body orifice or through the surface of the body. Classification here turns heavily on duration of use (see below) and on whether the invasive route is surgical.
Rules 9–13	Active devices	Devices whose operation depends on a source of energy other than that generated by the human body or gravity. Rule 13 (devices incorporating a medicinal substance with an action ancillary to that of the device) sits at the boundary of this group.
Rules 14–22	Special rules	Categories that do not fit cleanly into the three groups above: devices incorporating a medicinal substance as an integral part (Rule 14), devices used for contraception or prevention of sexually transmitted disease (Rule 15), devices specifically for disinfecting/cleaning other devices (Rule 16), devices manufactured from tissues/cells of human or animal origin (Rules 17–18), devices incorporating or consisting of nanomaterial (Rule 19, classified by the potential for internal exposure), invasive devices for administering medicinal products by inhalation (Rule 20), devices composed of substances absorbed by or dispersed in the body (Rule 21), and active therapeutic devices with an integrated diagnostic function that materially determines patient management (Rule 22).

Duration of use: the variable that does the most work

Within the non-invasive and invasive rule groups, MDR defines three duration bands, and which band a device falls into is frequently the single fact that moves it from one class to another:

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

The same physical device can sit in different classes depending on the intended-use duration a manufacturer actually claims — a short-term corrective contact lens (Class IIa) and a long-term corrective lens intended for extended wear are a real illustration of this: duration alone, not any change in the physical product, is what moves the classification.

The governing principle when more than one rule applies

A single device frequently satisfies more than one rule — a combination product, or a device with more than one intended function. Annex VIII’s implementing rules resolve this directly: where several rules apply to the same device based on its intended purpose, the strictest classification applies. The same principle governs a device with multiple intended purposes: if different parts of the device, or different intended purposes of the same part, would separately classify into different classes, the device as a whole is classified under whichever rule produces the highest class. This is a deliberate risk-conservative default, not an edge case to work around — the classification rationale document (see below) is exactly where a manufacturer has to show which rules were considered and why the resulting class is correct, not merely defensible.

Producing the classification rationale

MDR does not accept “we decided” as a classification basis. Article 51 and Annex VIII require a manufacturer to hold a documented classification rationale as part of the technical documentation, and MDCG 2021-24 (the Medical Device Coordination Group’s guidance on classification) is the reference most regulatory-affairs teams actually work from when applying the rules to a borderline or combination device, because the Annex VIII text itself is deliberately general rather than exhaustively worked-example driven. The rationale needs to state, in order: what the device’s intended purpose is (the classification starting point, not an afterthought — see CASRAI’s device-definition guide above), which rule or rules from Annex VIII apply given that intended purpose and the device’s physical/duration characteristics, and, if more than one rule applies, which one governs and why it is the strictest. A Notified Body reviewing a IIa/IIb/III submission checks this rationale directly; an incomplete or circular one (stating the class without showing the rule-by-rule reasoning that produced it) is a recurring, avoidable finding.

Once a device’s class is established, the conformity-assessment route, the Notified Body’s role (if any), and the clinical-evidence burden all follow from it — see CASRAI’s guides to Class IIa requirements, Clinical Evaluation Reports under EU MDR, Notified Body designation and audits, and EUDAMED registration for what happens after classification is settled. For the underlying quality system a device manufacturer runs regardless of class, see CASRAI’s ISO 13485 guide and ISO 13485 certification guide.

Frequently asked questions

Is EU MDR device classification the same as IVDR classification?

No. IVDR 2017/746 governs in vitro diagnostics under an entirely separate rule set (seven rules producing Classes A through D, the inverse risk ordering from MDR’s I-through-III), because diagnostics fail differently from therapeutic/implanted devices — the risk that matters is a wrong result driving a wrong clinical decision, not direct physical harm from the device itself. See CASRAI’s IVDR requirements guide for the IVDR-specific rules.

Does the device’s duration-of-use claim in labeling actually control its classification?

Yes, for the non-invasive and invasive rule groups specifically. The transient/short-term/long-term bands are defined by the manufacturer’s own intended continuous-use duration, which is why the intended-purpose statement has to be precise and consistent with what the device is actually labeled and instructed for — a mismatch between the claimed duration and real-world use is a classification-integrity problem, not just a labeling one.

Who has the final say on a device’s class — the manufacturer or the Notified Body?

The manufacturer makes the initial classification and owns the documented rationale, but for any class above Class I (self-certified), the Notified Body reviewing the conformity-assessment submission independently evaluates whether the claimed class is correct under Annex VIII, and a competent authority can challenge it. A manufacturer cannot simply assert a lower class to avoid Notified Body involvement; the rationale has to hold up to that independent review.