Liner Notes
UDI Labels: What Your Label Printer Needs From You
To print a UDI barcode that scans, verifies, and fits the label, your printer needs the approved issuing agency, identifier fields, symbology, size requirements, and grade target. Your regulatory team owns the UDI data; the label printer owns how accurately and reliably that data is reproduced on your medical and pharmaceutical labels. UDI problems at the press often trace back to details missing from the handoff.
Your team defines the UDI, and your label printer reproduces it
The UDI on your label belongs to your team, and the label printer's role is to reproduce it accurately.
The device maker chooses an FDA-accredited issuing agency (GS1, HIBCC, or ICCBBA), assigns a device identifier to each version and package level, decides what production data the label carries, and submits records to GUDID. Regulatory counsel decides what the label must say, which we cover in what belongs on a medical or pharmaceutical label. The label printer handles print method, facestock and adhesive, symbol size, proofing, and consistency from run to run.
FDA's 2013 final rule placed these requirements in 21 CFR Part 801 Subpart B and Part 830. The US compliance dates for each device class have passed, so the work now is getting labels right on each new SKU and revision.
A label printer that knows the structure well enough to question a value is useful, and the decision still sits with your regulatory team. We weigh in on how a code will print and scan. Before a job goes out, confirm who on your side owns the UDI data and signs off on proofs.
A UDI pairs a fixed device identifier with production data that changes run to run
A UDI has two parts: the device identifier (DI), which stays fixed for a given device version and package, and the production identifier (PI), which changes with each lot or unit. On press, the DI sits still and the PI moves.
Each package level gets its own device identifier
The DI names the labeler and the specific version or model, and it also names the package. Different device versions and package configurations may require different DIs under the applicable issuing-agency and FDA rules.
That means the unit, inner package, and case may not all use the same identifier. Your regulatory team should provide the approved DI for each package level included in the job.
Lot, serial, and dates make up the production identifier
The PI carries whichever of these apply to your device: lot or batch number, serial number, expiration date, and manufacturing date, plus the distinct identification code for HCT/P (human cells, tissues, and cellular and tissue-based products). Which fields appear is a decision for you and your regulatory team. We need to know which ones, in what order, and which column in your system holds each value.
The plain-text line must match the barcode character for character
Under 21 CFR 801.40, the UDI appears in plain text and in AIDC (automatic identification and data capture) form, usually a barcode. When both come from the same data, they match.
When someone types the plain text by hand, a transposed digit can slip in. Compare the two line by line at proof.
A GS1 UDI is built from labeled data fields, not one long number
When GS1 is the issuing agency, the barcode is built from Application Identifiers (AIs) that tell the scanner what each value means. Common UDI fields include the GTIN, lot or batch number, serial number, manufacturing date, and expiration date.
An illustrative UDI might contain:
- (01) GTIN / Device Identifier
- (10) Lot or batch
- (11) Manufacturing date
- (17) Expiration date
- (21) Serial number
Not every device uses every field. Your regulatory and quality teams determine which production identifiers apply; the label printer needs the approved fields, their order, and the source data for each one.
The important handoff is not a finished string typed into an email. Send the approved identifier structure and a sample data file so the barcode and human-readable information can be generated consistently from the same source.
Barcode dates and printed dates may use different formats
A date inside a GS1 barcode is encoded according to GS1 rules. For example, Application Identifiers such as (11) for manufacturing date and (17) for expiration date use a compact YYMMDD structure.
The same date may appear elsewhere on the device label in a different human-readable format required by the applicable labeling rules. That is why the safest workflow starts with one approved source date and generates each required representation from it rather than retyping dates in multiple places.
Tell us which date fields belong in the barcode, which also print separately as text, and which format your approved artwork requires.
A barcode can scan and still separate the data incorrectly
Some GS1 data fields have fixed lengths; others, such as lot and serial fields, can vary in length. When a variable-length field is followed by another field, GS1 uses a separator so the scanner knows where one value ends and the next begins.
In GS1 DataMatrix, that structure relies on the FNC1 character. If the separator is missing or placed incorrectly, a scanner may still decode the symbol but combine two fields into the wrong value.
Barcode software normally handles the FNC1 automatically. What we need from you is the approved field structure and order. We can then build the encoded data correctly and show the decoded result during proof review.
Tell us which issuing agency you use before we build the barcode
GS1 is not the only FDA-accredited UDI issuing agency. HIBCC and ICCBBA use different identifier structures and data carriers, so a barcode cannot be built correctly from the phrase “UDI label” alone.
Put the issuing agency at the top of the specification or RFQ. If it is GS1, send the approved GTIN and production-identifier structure. If it is HIBCC or ICCBBA, send the identifier and data structure approved under that system.
Liberty's role is to reproduce the approved structure accurately, not to choose the issuing system for you.
GS1 DataMatrix is often useful when label space is limited
When GS1 is the issuing agency, GS1 DataMatrix is commonly used on small device labels because it can carry multiple UDI data fields in a compact 2D symbol. GS1-128 carries GS1 data in a linear format and requires considerably more horizontal space.
FDA does not prescribe one universal barcode symbology for every UDI application, so the appropriate carrier depends on the issuing-agency rules, package level, available space, and your approved specification.
Whatever symbol you use, reserve enough room for its required X-dimension, quiet zone, and print tolerances before the artwork gets crowded.
How small can a UDI barcode print? How small a UDI barcode can print depends on the symbology, available label space, print method, material, and required verification grade. Rather than shrinking the code to fit a crowded layout, reserve the barcode area early and confirm that the available space supports the approved specification.
Shrinking the code to fit a crowded layout tends to cost more than it saves. Reserve the space at artwork stage.
What should I send? Your label dimensions, the area reserved for the code, and any minimum size or quiet zone your trading partners set. We'll weigh in on whether that space suits a GS1 barcode on your chosen material, finished in rolls, sheets, or continuous fanfold.
A scanner that beeps has not graded the barcode
A handheld scanner that beeps has confirmed the barcode decoded once, on that reader, under that light. A verifier grades the symbol against ISO/IEC 15415 for 2D symbols such as GS1 DataMatrix, or ISO/IEC 15416 for linear symbols such as GS1-128. It measures contrast, edge definition, quiet zone, and other parameters, then reports a letter or numeric grade.
A code can decode today and still grade poorly. That matters because the same symbol may encounter different readers, distances, lighting, and operating conditions throughout the supply chain.
A merged lot and serial field from the FNC1 example can also pass a scan while carrying the wrong data, so the proof review counts alongside the grade. A beep test is a fine sanity check and a poor acceptance criterion.
The grade target belongs to you and your trading partners. Put it in writing on the PO or spec, along with the standard it's measured against. For a deeper look at verification grades, contrast, quiet zones, ribbon/media matching, and other causes of scan failures, see our guide to why barcodes won't scan.
Reprocessed reusable devices may need the UDI marked on the device itself
Some reusable devices require direct marking on the device itself rather than relying only on package labels. Whether that requirement applies belongs with your regulatory team. Direct marking is a separate process from the label work Liberty provides, but package-level UDI labels still need the approved DI and PI structure.
Who does the marking? Usually a laser or similar process on metal or plastic. That's separate from label printing, a different supplier conversation, and work we don't do.
What about the packaging? Package labels still carry their UDIs, and that part stays in this handoff. Send the package-level DIs and PI structure even when the device itself is marked elsewhere.
Thermal transfer, inkjet, and digital handle variable UDI data differently
Thermal transfer, inkjet, and digital printing each handle changing lot, serial, and date data in their own way, and the right fit depends on facestock, environment, and run size.
Thermal transfer suits variable data on paper and film facestocks and is common where lot and serial change on each label. Our direct thermal vs. thermal transfer guide compares the two. Direct thermal is worth testing carefully wherever heat, abrasion, chemicals, or long retention could affect the image.
Digital printing may be the right choice when content changes across a run. Flexographic printing covers static content such as logos and fixed text, and it's often paired with a variable print step.
Whichever method runs, the data file shapes most UDI jobs. Send it the way your system exports it and name the column that holds each field. Confirm leading zeros and date formats, because "0001" and "1" look the same to a person and different to a database.
Before the run, we send a proof showing the first and last records plus a few from the middle. Check those against your source.
Cryogenic, permanent, removable, and all-temperature adhesives, plus UV coating or laminate, are options we discuss once we know where the label lives. If the finished label will go through steam, EtO, or gamma sterilization, the print system and construction should be validated for that cycle.
Changing UDI content means a labeling change under your quality system
Changing UDI content, whether a new DI, an added PI field, or a code moved on the layout, is a labeling change under your own quality procedures, and those procedures govern it. On our side, artwork is revision-controlled and any revision gets a new proof.
Change control is documented on our side too, with lot-level traceability and structured CAPA (corrective and preventive action), so a revision is tracked from proof to run.
A packaging change can affect the approved DI, even when the device itself has not changed. Before reusing an existing label file after a pack-count or package-level change, confirm the identifier with your regulatory team. If the DI changes, treat it as a new artwork revision and proof.
Ten answers to send with your UDI label artwork
Ten answers cover most of what a label printer needs for a UDI job, and they're the same questions we ask before quoting.
- Issuing agency, since it sets the whole structure of the string.
- The DI for each package level, so each label file carries the right one.
- PI fields and their order, which decides where separators go.
- Symbology, whether GS1 DataMatrix, GS1-128, or an HIBC symbol.
- Minimum barcode size and quiet zone, from your spec or trading partners.
- Grade target and the ISO/IEC standard it's measured against.
- Label dimensions and the package or surface the label goes on.
- The environment it must survive, such as cold storage, chemical exposure, or rough handling.
- Data file format, plus a sample file with your real column names.
- Scanners or readers used in the field, so size and contrast suit them.
Quick answers on UDI rules, GTINs, and printers
These six questions come up often when device teams prepare a UDI label job.
Who is responsible for creating the UDI?
The device manufacturer or labeler and its regulatory team own the UDI structure, issuing-agency relationship, device identifiers, production-identifier requirements, and GUDID records. The label printer should reproduce the approved data accurately and help ensure the symbol fits, prints, scans, and survives the intended environment.
What information does a label printer need before quoting a UDI label?
Provide the issuing agency, DI for each package level, required PI fields, symbology, label dimensions, barcode-size and grade requirements, data-file format, substrate or package, and the conditions the label has to survive. A sample data file is especially useful for variable-data jobs.
Do I need a special printer for UDI labels?
Not necessarily. The right print method depends on the label material, symbol size, variable-data requirements, run length, and environment. What matters is that the chosen process produces the approved data consistently at the required barcode quality.
What is the difference between UDI and GTIN?
A UDI is the regulated identification system for a medical device. When GS1 is the issuing agency, a GTIN commonly serves as the Device Identifier portion of the UDI. Other FDA-accredited issuing agencies use different identifier structures.
Why can a UDI barcode scan but still fail verification?
A scanner only confirms that one reader decoded the symbol. Verification measures print quality against the applicable ISO/IEC standard. A symbol can decode successfully and still have weak contrast, modulation, quiet-zone, or dimensional performance that produces a poor grade.
Who approves the final UDI proof?
Your regulatory or quality team should approve the identifier, human-readable text, data fields, and package-level assignment. Liberty can check printability, encoded structure, symbol quality, layout, and production consistency, but the approved UDI content remains yours.
Send the checklist, even half finished, and we'll flag the gaps before the first proof
Send the checklist with whatever answers you have. The team reviewing your first spec is the same team handling your reorders, with direct access to the people who make decisions.
Our people bring deep, technical expertise from combined label industry experience, and there's no minimum order quantity. Start on the Request a Quote page.
