I Can See Clearly Now: FDA Issues Final Guidance on the Form and Content of the Unique Device Identifier

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Channeling Johnny Nash and the 1972 classic song, “I Can See Clearly Now,” on July 7, 2021, the Food and Drug Administration issued its final guidance titled, “Unique Device Identification System: Form and Content of the Unique Device Identifier (UDI).”1  The UDI System Final Rule, which was issued almost eight years ago, was intended to create a standardized identification system for medical devices that adequately identifies them through distribution and use.2  The agency released a draft guidance five years ago. It is FDA’s expectation that the guidance, along with the Final Rule, will assist labelers and FDA-accredited issuing agencies in complying with UDI labeling requirements by clarifying the agency’s interpretation of certain requirements set forth in 21 C.F.R. § 801.40.3

This Bulletin summarizes some of the final guidance’s key provisions and provides background information for context.


  • The UDI Rule requires the label and package of every medical device to bear a UDI, unless an exception or alternative applies.
  • Some devices are required to bear a permanent marking providing the UDI on the device itself if the device is intended to be used more than once and intended to be reprocessed before each use.
  • The UDI Rule includes special labeling requirements for stand-alone software regulated as a device.
  • The guidance describes the two forms of a UDI (easily readable plain-text form and the automatic identification and data capture (AIDC) technology form), clarifies the content of the UDI, addresses the use of data delimiters that identify specific data elements within the UDI, and recommends the order in which the data should be presented in the easily readable plain-text form of the UDI carrier.

Unique Device Identifier (UDI)

  • A “Unique device identifier” is an identifier that adequately identifies a device through its distribution and use by meeting certain regulatory requirements.
  • A UDI is a device identifier (DI) and a production identifier (PI).
    • A “Device Identifier” is defined as “a mandatory, fixed portion of a UDI that identifies the specific version or model of a device and the labeler of that device.”
    • A “Production identifier” is defined as a “conditional, variable portion of a UDI” that identifies one or more of the following when included on the label of the device:
      • the lot or batch within which a device was manufactured;
      • the serial number of a specific device;
      • the expiration date of a specific device;
      • the date a specific device was manufactured;
      • for human cells, tissues, and cellular and tissue-based products regulated as a device on the distinct identification code.
  • A UDI must be issued under a system operated by an FDA-accredited issuing agency and conform to certain specific international standards incorporated by reference in the UDI Rule.
  • The UDI on the device label and packages must be provided in both easily readable plain-text and AIDC technology forms.
  • AIDC is defined as any technology that conveys the UDI or the DI portion of a UDI of a device in a form that can be entered into an electronic patient record or other computer systems through an automated process.

Data Delimiters

  • A “data delimiter” is a defined data character or a set of data characters that identify specific data elements within an encoded data string represented in the UDI carrier.
  • Data delimiters are used to identify the information that immediately follows them, and data delimiters vary based on the UDI system established by each FDA-accredited agency.
  • Data delimiters are important to UDI comprehensibility and use and distinguishes each data element within the data string represented in the UDI carrier.

Order of the Data

  • In the easily readable plain-text form of the UDI carrier, the UDI should precede any non-UDI elements.
  • The DI should go first, followed by the PI, if any.

Stand-Alone Software

  • The guidance included a new section offering recommendations for labeling requirements for stand-alone software.
  • FDA suggests that, for stand-alone software that is not distributed in packaged form, UDI labeling requirements are met if the UDI is provided through an easily readable plain-text statement displayed whenever the software has started or an easily readable plain-text statement displayed through a menu (or both).
  • The agency adds that PI must also convey the stand-alone software’s version number.


[1] Available at https://www.fda.gov/media/99084/download.

[2] See 78 Fed. Reg. 58,786 (September 24, 2013).

[3] Guidance at 1.