The 22 classification rules
Schedule 2 of the Medicines (Database of Medical Devices) Regulations 2003 sets out 22 rules for classifying non-IVD medical devices. Rules are grouped into four categories.
Apply all potentially relevant rules to your device. If more than one rule gives a different classification, the highest class applies.
Rules 1–4 — Non-invasive devices
| Rule | Summary | Default class |
|---|---|---|
| Rule 1 | All non-invasive devices not covered by Rules 2–4 | Class I |
| Rule 2 | Channelling or storing blood, body fluids, cells, or liquids for infusion | Class IIa |
| Rule 3 | Modifying biological or chemical composition of blood, tissues, or cells; or in contact with injured skin | Class IIa or IIb depending on intended use |
| Rule 4 | Contact with injured skin as a wound dressing | Class I, IIa, or IIb depending on depth and condition |
Rules 5–8 — Invasive devices
| Rule | Summary | Default class |
|---|---|---|
| Rule 5 | Invasive devices for body orifices — transient use | Class I |
| Rule 6 | Invasive devices for body orifices — short-term use; surgically invasive transient devices | Class IIa |
| Rule 7 | Surgically invasive devices — short-term use | Class IIa or IIb |
| Rule 8 | Implantable devices and long-term surgically invasive devices | Class IIb or III |
Rules 9–12 — Active devices
| Rule | Summary | Default class |
|---|---|---|
| Rule 9 | Active therapeutic devices intended to exchange energy | Class IIa or IIb |
| Rule 10 | Active devices for diagnosis | Class IIa (with some Class I and IIb exceptions) |
| Rule 11 | Software intended to provide information for diagnosis or treatment decisions | Class IIa (or higher if failure could be catastrophic) |
| Rule 12 | Active devices intended to administer or exchange energy in a potentially hazardous way | Class III |
Rules 13–18 — Special rules
| Rule | Summary | Class |
|---|---|---|
| Rule 13 | Devices incorporating a medicinal substance | Class III |
| Rule 14 | Devices used for contraception or STI prevention | Class IIb or III |
| Rule 15 | Devices specifically intended for disinfection of other medical devices | Class IIa or IIb |
| Rule 16 | Devices specifically for recording X-ray images | Class IIa |
| Rule 17 | Devices manufactured from biological origin (animal tissue or derivatives) | Class III |
| Rule 18 | Blood bags | Class IIb |
Rules 19–22 — Additional rules
| Rule | Summary | Class |
|---|---|---|
| Rule 19 | AIMDs — active implantable medical devices | AIMD class |
| Rule 20 | Devices that incorporate a substance that, used separately, would be a medicinal product and has action ancillary to the device | Class III |
| Rule 21 | Devices used for birth control or STI prevention (not covered by Rule 14) | IIb |
| Rule 22 | Nanomaterial-based devices | Depends on intended use and potential for internal exposure |
Worked example
Device: A single-use catheter inserted through the urethra for a procedure lasting approximately 45 minutes.
- Is it non-invasive? No — it enters a body orifice
- Rule 5 — invasive, body orifice, transient use (≤60 min) → Class I
- But Rule 6 — short-term (>60 min, ≤30 days) would give IIa
- Duration is ~45 min → transient → Rule 5 → Class I
If the same catheter was left in for 2 hours, it would fall under Rule 6 → Class IIa.
For complex classification decisions, consult the Medsafe guidance document on classification and the GHTF/SG1/N015:2006 guidance on medical device classification, which Medsafe references in its framework.
For Rule 22, nanomaterial-based devices are assessed for potential systemic absorption or migration of nanoparticles. Devices with direct or prolonged contact with body surfaces or internal tissues, or those designed to release nanoparticles, face higher scrutiny. Consult Medsafe's nanomaterial guidance or seek technical advice if this rule may apply.