How classification works
Classification rules for general medical devices are in Schedule 2 of the UK MDR 2002 (Part I). AIMD classification is in Part II. IVD classification is in Annex II of Part III. Classification determines the conformity assessment route, whether a UK Approved Body is required, the depth of clinical evidence needed, and post-market obligations.
This site provides general information only and does not constitute legal or regulatory advice. Always consult the official legislation text and a qualified regulatory professional before making classification decisions.
Why classification matters
Classification is the first and most consequential regulatory decision a manufacturer must make. The device's class determines:
- Which conformity assessment route applies
- Whether a UK Approved Body (UKAB) must be involved — and in what capacity
- The depth of clinical or performance evidence required
- MHRA registration details and documentation required
- Post-market obligations including PSUR frequency and PMS requirements
- The scope of labelling and IFU requirements
Getting classification wrong has real consequences. Under-classifying a device risks placing an inadequately assessed product on the GB market. Over-classifying wastes resources and delays patient access. MHRA can challenge classification during market surveillance, and UKABs may challenge it during conformity assessment.
Three separate classification systems
UK MDR 2002 contains three separate classification frameworks, one for each Part:
| System | Classes | Device type | Legal basis |
|---|---|---|---|
| Part I | Class I, IIa, IIb, III | General medical devices | Schedule 2, UK MDR 2002 |
| Part II | AIMD (single category) | Active implantable medical devices | UK MDR 2002 Part II |
| Part III | List A, List B, Self-test, General | IVD medical devices | Annex II, UK MDR 2002 Part III |
These systems are separate — a Class IIa general medical device is not equivalent to a List B IVD, even though both require UKAB involvement.
General medical devices — Classes I, IIa, IIb, III
Classification of general medical devices under Part I of UK MDR 2002 is rule-based, applying the classification rules in Schedule 2. These rules are organised by the device's interaction with the human body.
The risk hierarchy
| Class | Risk level | UKAB required? | Examples |
|---|---|---|---|
| Class I | Lowest risk | No (except sterile, measuring, or reusable surgical instruments) | Bandages, tongue depressors, non-sterile gloves, wheelchairs |
| Class IIa | Low-to-medium risk | Yes | Hearing aids, surgical sutures, dental fillings, short-term surgically invasive devices |
| Class IIb | Medium-to-high risk | Yes | Ventilators, infusion pumps, long-term implantable devices (non-cardiac) |
| Class III | Highest risk | Yes (full assessment) | Coronary stents, hip implants, spinal disc replacements, heart valves |
Class I sub-categories
Class I is not monolithic. Three sub-categories of Class I device require UKAB involvement for specific aspects of conformity assessment:
| Sub-category | UKAB involvement |
|---|---|
| Class I (sterile) — devices placed on the market in a sterile condition | UKAB assesses the sterility aspects only |
| Class I (measuring) — devices with a measuring function | UKAB assesses the metrology aspects only |
| Class Im — reusable surgical instruments | UKAB assesses the reprocessing aspects only |
Even within these sub-categories, the manufacturer self-declares conformity for the non-UKAB aspects.
How the classification rules work
Schedule 2 of UK MDR 2002 contains 18 classification rules (Rules 1–18). They are applied as follows:
Step 1 — Determine fundamental characteristics:
- Is the device invasive (penetrates body surface or orifice)?
- Is it surgically invasive (introduced through a surgical incision)?
- Is it active (depends on energy other than gravity or the human body)?
- What is the duration of use — transient (<60 min), short-term (60 min–30 days), long-term (>30 days)?
- Is it implantable?
Step 2 — Apply the relevant rules:
| Rule group | Scope |
|---|---|
| Rules 1–4 | Non-invasive devices |
| Rules 5–8 | Invasive devices |
| Rules 9–12 | Active devices |
| Rules 13–14 | Special rules (substances administered to the body, devices used with medicines) |
| Rule 15 | Devices used for contraception or prevention of STIs |
| Rule 16 | Devices specifically for disinfecting, cleaning, or rinsing contact lenses |
| Rule 17 | Devices for recording diagnostic images |
| Rule 18 | Devices incorporating non-viable animal tissue or cells |
Step 3 — Where multiple rules apply: If more than one rule results in a different class, the highest class prevails.
Step 4 — Document the rationale: The classification rationale, including which rules were applied and why, must be documented in the technical file.
Rule 9 to Rule 12 cover active devices — including software. Rule 12 specifically addresses active devices intended to diagnose or monitor vital physiological processes. Many AI/SaMD products fall here. See Software & AI as a medical device for the full software classification logic.
Active implantable medical devices (AIMDs)
Active implantable medical devices are governed by Part II of UK MDR 2002 rather than Part I. AIMDs are devices:
- Intended to be totally or partially introduced, surgically or medically, into the human body, or by medical intervention into a natural orifice, and
- Which are intended to remain after the procedure, and
- Which depend for their functioning on a source of electrical energy or any source of power other than that directly generated by the human body or gravity.
Examples: pacemakers, implantable cardioverter-defibrillators (ICDs), cochlear implants, implantable neurostimulators.
AIMDs have a single risk tier — there are no sub-classes. All AIMDs require full UKAB assessment (equivalent to a Class III conformity assessment process). The Essential Requirements for AIMDs are in Part II, Schedule 1 of UK MDR 2002.
IVD medical devices — List A, List B, Self-test, General
IVD classification under Part III of UK MDR 2002 does not use the same I/IIa/IIb/III class structure. Instead, it uses a list-based system:
| Category | Risk | UKAB required? | Basis |
|---|---|---|---|
| Annex II List A | Highest | Yes — design dossier + production QA | Explicitly listed in Annex II List A |
| Annex II List B | Significant | Yes — type examination or QA | Explicitly listed in Annex II List B |
| Self-test | Variable | Yes — specific to self-test requirements | Intended for use by lay persons |
| General IVDs | Lowest (regulated) | No — self-declaration | All IVDs not in Lists A, B, or Self-test |
Annex II List A — highest-risk IVDs
All devices in List A require a full UKAB assessment including:
- EC Design Examination (design dossier review)
- Production Quality Assurance
Current List A devices include reagents for HIV 1&2, HTLV I&II, Hepatitis B/C/D, ABO blood grouping, Rh (anti-D, anti-C, anti-c, anti-E, anti-e) blood grouping, Kell, Kidd, Duffy systems, and anti-Kell reagents.
Annex II List B — significant-risk IVDs
List B devices require UKAB involvement, though through a less intensive route than List A.
Current List B devices include reagents for rubella, toxoplasma, CMV, PKU, congenital hypothyroidism, hCG (professional pregnancy testing), PSA, blood glucose (professional use), haemoglobin determination.
Self-test devices
Any IVD specifically designed for use by lay persons in a home setting — regardless of its analyte — is a self-test device and requires specific:
- UKAB assessment
- Lay-person-oriented labelling
- Simplified IFU in plain language
- Usability data demonstrating the device can be correctly used by an untrained person
General IVDs
All IVDs not listed in Annex II and not intended as self-test devices are "general IVDs." Manufacturers self-declare conformity and affix the UKCA mark without UKAB involvement.
Key difference from EU IVDR classification
Manufacturers accessing both GB and EU markets must manage two separate IVD classification systems:
| Framework | Classification |
|---|---|
| UK MDR 2002 Part III (GB) | List A / List B / Self-test / General — derived from IVDD 98/79/EC |
| EU IVDR 2017/746 (EU + NI) | Class A / B / C / D — new risk-based system |
Many IVDs that were "General" under IVDD — and remain "General" under UK MDR 2002 Part III — have been upclassified to Class B or Class C under EU IVDR. These devices now require EU Notified Body involvement for the EU/NI market, even though they remain self-declaration products for the GB market.
Manufacturer's responsibility for classification
Classification is the manufacturer's responsibility. Unlike the US FDA, there is no pre-submission or pre-market classification determination process in the UK MDR 2002 framework — MHRA does not formally approve classification decisions before market placement.
However:
- UKABs review and may challenge classification as part of conformity assessment
- MHRA can challenge classification during market surveillance
- Manufacturers can seek informal guidance from MHRA's pre-submission service
If a UKAB disagrees with a manufacturer's classification, the manufacturer must either revise their classification or provide a substantiated rationale. If disputes persist, MHRA can make a determination.
Related pages
- Class I · IIa · IIb · III — overview of each class
- Classification rules — Schedule 2 in detail
- IVD classification — List A · List B · Self-test · General
- Active & implantable devices
- Software & SaMD classification
- Borderline & combination products
Official references
| Reference | Description |
|---|---|
| UK MDR 2002, Schedule 2 | Classification rules for general medical devices (Part I) |
| UK MDR 2002, Part II | Active implantable medical devices |
| UK MDR 2002, Part III, Annex II | IVD classification lists A and B |
| MHRA guidance: Classification of medical devices | MHRA guidance on applying the classification rules |
| MHRA guidance: IVD medical devices | IVD-specific classification guidance |
| MDCG 2021-24 (reference) | EU software classification guidance — useful comparative reference |