Written and maintained by CASRAI Editorial Board
Last updated
General regulatory information for lab, clinic and supply staff; not legal or medical advice. Last checked against the sources below on 2026-11-01.
Short answer
A Basic UDI-DI is the EU MDR identifier that groups devices with the same intended purpose, risk class and essential design and manufacturing characteristics. It is the main key in the EU database and in the device’s regulatory documents, and it does not appear on the label or any trade item. If you need to find it, look at the declaration of conformity or certificate, not the box.
Definition and scope
MDCG 2018-1 Rev.4 describes the Basic UDI-DI as the main key in the database and in relevant documentation (certificates, declaration of conformity, technical documentation and the summary of safety and clinical performance) used to connect devices that share an intended purpose, risk class and essential design and manufacturing characteristics. The European Commission’s UDI Q&A calls it the main access key for device-related information in the Eudamed database (see our EUDAMED guide for the modules).
The manufacturer assigns the Basic UDI-DI together with the UDI and registers it in Eudamed. The Commission’s Q&A notes that within the EU the manufacturer assigns a Basic UDI-DI in addition to the UDI, something not yet required by other jurisdictions. The UDI system covers all devices except custom-made devices and performance study or investigational devices. A system or procedure pack producer assigns a Basic UDI-DI to the pack.
How it is used in practice
Because the Basic UDI-DI is independent of packaging and labelling, it works as a documentation key rather than a scanning identifier. The same value ties together the regulatory paperwork for a family of devices, while each individually labelled presentation carries its own UDI-DI.
Where the Basic UDI-DI appears, and where it does not
| Document or place | Basic UDI-DI present? | What MDCG 2018-1 Rev.4 says |
|---|---|---|
| Label, packaging or any trade item | No | It is independent of the packaging and labelling and does not appear on any trade item. |
| Declaration of conformity (Annex IV) | Yes | Must contain the Basic UDI-DI together with the product and trade name, product code, catalogue number or other unambiguous reference. |
| Certificates (Annex XII) | Yes | The certificate scope includes the Basic UDI-DI with the name, model, type, intended purpose and risk classification, and covers all devices associated with that Basic UDI-DI. |
| Technical documentation and summary of safety and clinical performance | Yes | Named as relevant documentation that is connected through the Basic UDI-DI. |
| Eudamed | Yes | The main access key for device information (European Commission UDI Q&A). |
For a buyer or regulatory assistant this gives a practical check: the Basic UDI-DI on a supplier’s declaration of conformity or certificate should be the one the certificate scope covers. Our guides on CE certificate verification and EU MDR technical documentation cover those documents in more depth.
Basic UDI-DI, UDI-DI and UDI-PI
The UDI-DI identifies a specific version or presentation of a device and is the part that is labelled; the UDI-PI is the variable production part (see UDI-PI and UDI labels). MDCG 2018-1 Rev.4 states that a UDI-DI is associated with one and only one Basic UDI-DI. Several UDI-DIs can therefore sit under one Basic UDI-DI, but never the reverse.
When a UDI-DI changes
The guidance requires a new UDI-DI whenever a change could lead to misidentification of the device or ambiguity in its traceability. Changes it lists include:
- name or trade name;
- version or model;
- labelled as single use;
- packaged sterile;
- need for sterilisation before use;
- quantity in a package;
- critical warnings or contra-indications (for example latex or DEHP);
- CMR substances or endocrine disruptors.
A footnote adds that colour or language changes can also require a new UDI-DI, giving the examples of colour coding of connectors, latex-free surgical gloves and blood collection tubes. Exceptions are stated directly: a change in UDI-PI type with no label change does not need a new UDI-DI; a change in direct marking needs one only when it goes from Yes to No; and where a maximum number of reuses is established (Annex VI Part B, 17), changing it requires a new UDI-DI.
EU and US compared
| Item | EU (MDR) | US (FDA) |
|---|---|---|
| Device identifier | UDI-DI | DI: a mandatory, fixed portion of a UDI that identifies the labeler and the specific version or model of a device |
| Production identifier | UDI-PI | PI: a conditional, variable portion of a UDI |
| Group-level key | Basic UDI-DI | No Basic UDI-DI concept in the FDA UDI Basics page |
| Database | Eudamed holds the Basic UDI-DI | GUDID does not include the PI |
For the US submission workflow see UDI labeling and GUDID submission.
Where it matters for labs, clinics and supply decisions
A device sold in the EU carries documents keyed by the Basic UDI-DI, so a supplier file can be matched to a certificate scope without relying on the packaging. When a product changes in a way that triggers a new UDI-DI, the Basic UDI-DI may stay the same, so two items with different UDI-DIs can still share one declaration of conformity. Inventory records that store only the Basic UDI-DI cannot tell such presentations apart; the labelled UDI-DI can.
Common misunderstandings
- It is not a barcode value. It is not on the label or any trade item.
- It is not required by the US system. The FDA pages describe only the DI and PI.
- It does not cover everything. MDCG 2018-1 Rev.4 does not address reprocessed devices, systems or procedure packs, software, Annex XVI products, parallel trade or own-brand labelling.
- It is guidance, not law. The document is not legally binding; only the Court of Justice of the EU gives binding interpretations.
FAQ
Is the Basic UDI-DI on the label?
No. It is independent of the packaging and labelling and does not appear on any trade item (MDCG 2018-1 Rev.4).
Can one UDI-DI belong to two Basic UDI-DIs?
No. A UDI-DI is associated with one and only one Basic UDI-DI.
Who assigns the Basic UDI-DI?
The manufacturer, who also registers it in Eudamed. For a system or procedure pack the pack’s producer assigns it.
Is the Basic UDI-DI part of the US UDI system?
No. The FDA UDI Basics page describes the device identifier (DI) and the production identifier (PI) only, and the Commission Q&A says a Basic UDI-DI is not yet required by other jurisdictions.
Sources
- MDCG 2018-1 Rev.4, Guidance on BASIC UDI-DI and changes to UDI-DI, April 2021, European Commission: health.ec.europa.eu (checked 2026-11-01).
- European Commission, Introduction to the new UDI system and the obligations of operators (Q&A): health.ec.europa.eu (checked 2026-11-01; timelines in this older document not used).
- FDA, UDI Basics: fda.gov (checked 2026-11-01).
