Class I · IIa · IIb · III
Device classes for general medical devices are defined by the classification rules in Schedule 2 of the UK Medical Devices Regulations 2002 (Part I). Class determines the conformity assessment route under Schedule 3. Active implantable devices are governed by Part II (see AIMD). IVDs are classified separately (see IVD classification).
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 finalising classification decisions.
Overview: the four-class system
UK MDR 2002 Part I classifies general medical devices into four classes based on risk. Risk is assessed by reference to the device's intended purpose, its invasiveness, its duration of contact with the body, the body location it acts upon, and whether it is active (dependent on an energy source).
| Class | Risk level | UKAB required? | Conformity assessment route |
|---|---|---|---|
| Class I | Lowest | No — except sterile, measuring, or reusable surgical instruments | Self-declaration for most; UKAB for specific aspects |
| Class IIa | Low-to-medium | Yes | QMS audit (Annex II-equivalent) or type-examination |
| Class IIb | Medium-to-high | Yes | Full QMS audit; some require type-examination |
| Class III | Highest | Yes — full assessment | Full QMS + design dossier examination |
The highest applicable class always prevails — if more than one classification rule applies to a device and they produce different classes, the device falls into the higher class.
Class I — lowest risk
Definition
Class I devices are those that present the lowest individual and societal risk. They are typically non-invasive, or if invasive, intended only for transient use through body orifices without being surgically invasive.
Conformity assessment for Class I
For standard Class I devices, the manufacturer:
- Self-declares conformity with the Essential Requirements
- Issues a UK Declaration of Conformity
- Affixes the UKCA mark (or relies on CE marking under transitional acceptance)
- Registers with MHRA
No UK Approved Body involvement is required for standard Class I.
Class I sub-categories requiring UKAB
Three sub-categories of Class I require partial UKAB involvement:
| Sub-category | UKAB scope | Examples |
|---|---|---|
| Class I (sterile) — placed on the market in a sterile condition | UKAB assesses sterility aspects only (manufacturing and sterilisation QMS) | Sterile wound dressings, sterile single-use syringes, sterile irrigation solutions |
| Class I (measuring) — has a measuring function | UKAB assesses metrology aspects only | Graduated syringes, thermometers, non-electronic sphygmomanometers |
| Class Im — reusable surgical instruments | UKAB assesses information for reprocessing | Reusable scalpel handles, reusable forceps, reusable retractors |
For these sub-categories, the UKAB certificate covers only the aspect requiring third-party assessment. The manufacturer self-declares all other Essential Requirements.
Examples of Class I devices
- Non-sterile wound dressings and bandages
- Tongue depressors and spatulas
- Surgical gloves (non-sterile)
- Wheelchairs and walking frames
- Hospital beds and stretchers
- Non-electronic blood pressure cuffs (if no measuring function claimed)
- Magnifying glasses for clinical use
- Spectacle frames (lenses are Class IIa)
- Corrective contact lens cases (lenses are Class IIa)
- Examination lights
Class IIa — low-to-medium risk
Definition
Class IIa encompasses devices that have moderate potential for harm — typically because they are more invasive, remain in contact with the body for longer periods, or have a direct physiological effect.
Conformity assessment for Class IIa
Class IIa requires UK Approved Body involvement. The manufacturer must use one of the following conformity assessment routes (Schedule 3, UK MDR 2002):
- Annex II-equivalent (Full QMS): UKAB audits the manufacturer's QMS and reviews the technical documentation
- Annex III-equivalent (Type Examination) + Annex IV/V/VI-equivalent: UKAB examines a representative device specimen; manufacturer then demonstrates ongoing production conformity via QMS audit or product verification
The manufacturer issues a UK Declaration of Conformity referencing the UKAB certificate.
Examples of Class IIa devices
- Hearing aids (non-implantable)
- Dental fillings and cements
- Short-term surgically invasive devices (≤30 days, not in central circulatory or nervous system)
- Urinary catheters
- Tracheostomy tubes
- Blood glucose meters (professional use — also IVD List B consideration)
- Ultrasound imaging equipment
- MRI machines and X-ray equipment (diagnostic imaging)
- Surgical sutures and staples
- Spectacle lenses and corrective contact lenses
- Orthopaedic external fixators
- Non-active physiotherapy equipment
Class IIb — medium-to-high risk
Definition
Class IIb covers devices that present a higher potential for harm than Class IIa — typically those intended for long-term use inside the body (non-cardiac), those that modify or monitor vital physiological processes, or those connected to active devices that perform a critical function.
Conformity assessment for Class IIb
Class IIb requires UK Approved Body involvement with a more extensive assessment than Class IIa:
- Annex II-equivalent (Full QMS): UKAB audits the full QMS and reviews technical documentation for the entire device product line
- Annex III-equivalent (Type Examination) is also available for some Class IIb devices, followed by a production QMS or product verification module
For many Class IIb devices — particularly those with significant design complexity or patient risk — the Annex II (full QMS) route is preferable.
Examples of Class IIb devices
- Ventilators and anaesthesia machines
- Infusion pumps (including patient-controlled analgesia pumps)
- Surgical lasers
- Hip and knee implants (non-cemented — cemented joint replacements are Class III)
- Intraocular lenses (non-foldable anterior chamber lenses)
- Blood bags and blood circuit sets
- External cardiac pacemaker electrodes
- Long-term (>30 days) surgically invasive devices not in Class III
- Haemodialysis machines and dialysis fluid concentrates
- Diagnostic imaging contrast agents combined with delivery devices
- Neonatal incubators
Class III — highest risk
Definition
Class III is reserved for devices that present the highest level of patient or public risk — typically because they contact the central circulatory system or central nervous system, are long-term implants in critical anatomical locations, or pose a significant risk of harm if they fail.
Class III devices require the most rigorous conformity assessment — involving both a full QMS audit and examination of the device's design dossier.
Conformity assessment for Class III
Only one conformity assessment route is available for Class III under UK MDR 2002:
Annex II-equivalent (Full QMS) + Design Dossier Examination:
- UKAB audits the manufacturer's full QMS (design, manufacture, production, post-market)
- UKAB examines the design dossier (a subset of the technical file with additional design-stage information)
- UKAB issues a Design Examination Certificate covering the device design
- UKAB issues a QMS Certificate covering the quality system
- Manufacturer issues UK Declaration of Conformity referencing both certificates
- UKCA mark applied
Design dossier examination involves UKAB review of:
- Device description and specifications
- Design inputs and outputs
- Risk analysis
- Clinical evaluation
- Pre-clinical test results
- Proposed labelling and IFU
This is the most thorough conformity assessment route and typically takes the longest from application to certification.
Examples of Class III devices
- Coronary stents (drug-eluting and bare metal)
- Heart valves (mechanical and biological)
- Implantable cardioverter-defibrillators (ICDs) — though often also AIMD
- Coronary artery stent grafts
- Total hip and knee replacements (cemented)
- Spinal disc replacements and spinal implants in the spinal canal
- Implantable neurostimulators (central nervous system)
- Intravascular devices intended for >30 days in the circulatory system
- Blood contact devices with systemic circulatory contact
- Breast implants
- Vascular prostheses
- Drug-eluting wound dressings where drug action is ancillary
Moving between classes — key classification triggers
Several characteristics reliably push devices into higher classes:
| Characteristic | Classification effect |
|---|---|
| Contact with central circulatory system | Typically Class III |
| Contact with central nervous system | Typically Class III |
| Long-term implant (>30 days) in the heart, CNS, or circulatory system | Class III |
| Drug incorporated with ancillary role | Class III (or AIMD if active) |
| Active device diagnosing or monitoring vital physiological parameters | Class IIa or IIb |
| Software with direct influence on therapy or diagnosis of life-threatening conditions | Class IIb or III |
| Surgically invasive, short-term use, not in critical location | Class IIa |
| Surgically invasive, long-term, not in critical location | Class IIb |
Comparison with EU MDR classes
The UK classification structure (Classes I, IIa, IIb, III) closely mirrors the EU MDD-era structure on which UK MDR 2002 is based. However, the EU MDR 2017/745 introduced more classification rules (22 vs 18 in UK MDR 2002) and explicitly upclassified some device types. Notable differences:
| Device type | UK MDR 2002 class | EU MDR 2017/745 class |
|---|---|---|
| Spinal disc replacement | Class IIb | Class III |
| Joint replacement (metal-on-metal large head) | Class IIb | Class III |
| Non-corrective contact lenses | Not regulated as MD | Class III (Annex XVI) |
| SaMD for serious condition diagnosis | Class IIa–IIb | May be Class IIb or III |
| Nanomaterial devices | Case-by-case | Rule 19/21 — often upclassified |
Manufacturers must classify their devices independently under each framework for each market.
Related pages
- How classification works — Schedule 2 rule-by-rule application
- Classification rules — Schedule 2 in detail
- IVD classification — List A · List B · Self-test · General
- Active implantable devices (AIMD)
- Software & SaMD classification
- Conformity assessment overview
- UK Approved Bodies
Official references
| Reference | Description |
|---|---|
| UK MDR 2002, Schedule 2 | Classification rules for general medical devices |
| UK MDR 2002, Schedule 3 | Conformity assessment procedures by class |
| MHRA: Classification of medical devices | MHRA guidance on applying Schedule 2 rules |
| MHRA: Guidance on the UK Medical Devices Regulations 2002 | General guidance document |
| EU MDD 93/42/EEC Annex IX | Source of the UK Schedule 2 classification rules (for reference) |