How are medical devices classified under EU MDR?

MDR Annex VIII · MDCG 2021-24 · MDCG 2025-4

The short answer

EU MDR uses a four-class risk-based system (Class I, IIa, IIb, III). The class is determined by applying the 22 classification rules in Annex VIII to the device's intended purpose. Higher class means higher risk, stricter conformity assessment, and mandatory Notified Body involvement.

Classification overview

Class	Risk level	Examples	Conformity assessment
Class I	Low	Bandages, non-measuring software, wheelchairs	Self-certification (Declaration of Conformity)
*Class I (Is/Im/Ir)**	Low – specific aspects	Sterile (Is), measuring function (Im), reusable surgical (Ir)	Self-cert + Notified Body for sterility / measuring / reuse aspects
Class IIa	Medium	Dental fillings, hearing aids, diagnostic software	Notified Body — Annex IX or XI
Class IIb	Medium-high	Ventilators, infusion pumps, X-ray equipment	Notified Body — Annex IX or X
Class III	High	Heart valves, neurostimulators, high-risk SaMD	Notified Body — Annex IX + clinical evaluation consultation (Art. 54), or Annex X

How the 22 classification rules work

Annex VIII contains 22 rules grouped by device type. You apply each rule that is relevant to your device's intended purpose. Where more than one rule applies, the highest resulting class determines the overall classification.

Rules 1–4: Non-invasive devices
Rules 5–8: Invasive devices
Rules 9–13: Active devices (including Rule 11 for software)
Rules 14–22: Special rules (devices with specific purposes, e.g. contraceptive, spinal, breast implants)

The rule that produces the highest class governs. Classification must be documented with explicit rationale in the technical documentation.

Rule 11 — software classification

Rule 11 applies to software that is itself a medical device (SaMD) or software that controls or influences hardware medical devices. The class depends on the severity of harm that could result from a failure or erroneous output.

Software output / function	Class
Decisions causing death or irreversible deterioration of health	Class III
Decisions causing serious deterioration of health or requiring surgical intervention	Class IIb
Other diagnostic or therapeutic decision support (reversible outcomes)	Class IIa
No diagnostic or therapeutic decision support; patient management only	Class I

MDCG 2025-4 provides updated guidance on applying Rule 11 to AI/ML-enabled software and reinforces that classification is driven by the intended purpose, not by the technology used.

Common classification mistakes

Too narrow intended use: Describing intended use to achieve a lower class, while the device is used more broadly in practice
Relying on old MDD class: MDR classification rules differ from MDD — especially for software (Rule 11 vs. old rule 12)
Following a competitor's class: Classification is based on your device's specific intended purpose, not a competitor's
Not documenting rationale: The classification decision and the specific rules applied must be documented and traceable in the technical documentation

Frequently asked questions

Can I challenge a Notified Body's classification opinion?

Yes. If you disagree with a NB's classification, you can provide additional argumentation or request MDCG guidance. Ultimately, national competent authorities (NCAs) can issue binding classification decisions. EUDAMED captures the official class.

What changed with MDCG 2025-4?

MDCG 2025-4 updated the guidance on software classification under Rule 11, with specific attention to AI/ML systems, apps that inform clinical decisions, and the concept of "significant impact" on clinical outcomes. It replaces and refines earlier MDCG 2019-11 classification guidance.

Does a Class I device still need technical documentation?

Yes. All classes require Annex II technical documentation and the GSPR checklist, a QMS, PMS, and a Declaration of Conformity. Class I is self-certified, but the full documentation burden still applies.