Purpose
Medical device labels must be unambiguous, traceable, and machine-readable. This guide covers building UDI-carrying labels in Label Studio Creator: the GS1 DataMatrix / UDI structure, lot / serial / expiry, standard medical symbols, and the validation checks that keep every label scannable.
Layout and workflow guidance only — confirm exact obligations (EU MDR, US FDA UDI, your issuing agency) for your device class.
1. Understand the UDI structure
A UDI has two parts. Get the structure right and the rest follows:
- UDI-DI (device identifier): the fixed GTIN of the device model — GS1 AI
(01). - UDI-PI (production identifier): the variable part — expiry
(17), lot(10), serial(21), manufacture date(11). - Both are carried in a single GS1 DataMatrix (or GS1-128) and mirrored in human-readable text.
2. Build the data-carrier
Choose GS1 DataMatrix
Preferred for small medical surfaces; use Tools > Barcode Assistant and select GS1 DataMatrix (FNC1).
Compose the AIs
Concatenate (01)GTIN (17)expiry (10)lot (21)serial in the correct order and formats.
Bind variable PI
Point expiry/lot/serial at data fields so each unit gets its own PI automatically.
Add HRI text
Print the same values as human-readable text with the AIs shown in parentheses.
3. Standard medical symbols
| Symbol | Meaning |
|---|---|
| Factory + date | Manufacturer and date of manufacture. |
| Hourglass | Use-by / expiry date. |
| LOT / SN | Batch code / serial number. |
| “2” crossed | Do not reuse (single use). |
| Book / “i” | Consult instructions for use. |
| REF / UDI | Catalogue reference / unique device identifier. |
4. Validation checks
Medical labels demand hard validation. Before any release:
- Syntax: AIs present, in order, with correct fixed/variable lengths and FNC1 separators.
- Check digit: GTIN check digit valid.
- Formats: dates as
YYMMDDin the carrier; serial uniqueness. - Grade: print/scan quality (e.g. DataMatrix grade) on the real material.
- Match: HRI text equals encoded data, field by field.
5. Serial handling & reprints
Guarantee uniqueness
Serials must not repeat. Source them from a controlled sequence, not manual typing.
Reprint the same serial
If a unit's label is damaged, reprint that exact serial from history — never a fresh number.
Reconcile counts
Printed serials should match the produced units; investigate gaps.
Keep an audit trail
Record what was printed, when, and by whom for traceability.
6. Common problems and fixes
| Symptom | Likely cause & fix |
|---|---|
| Scanner rejects the code | Missing FNC1 / wrong AI order. Rebuild with the GS1 DataMatrix assistant. |
| HRI ≠ encoded data | Text typed separately. Bind HRI to the same fields as the carrier. |
| Low DataMatrix grade | Too small or low contrast on the material. Increase module size; retest. |
| Duplicate serials | Manual entry. Use a controlled serial source. |
| Wrong date format in carrier | Not YYMMDD. Fix the field format for AI (17)/(11). |