Units of Measure (UoM)

The UoM Project

Product Vision Statement

For producers and consumers of pathology diagnostics within the NHS

Who need safe reliable communication of diagnostic results for both human (clinician + patient) and computer interpretation.

The UoM project will analyse both the current state and future needs for describing units of measure in Pathology, in order to deliver a solution that meets the need for a fully computable pathology message structure, without compromising patient safety or usability for clinicians or patients.

Unlike current practice

The future UoM solution will support the FHIR and UTL projects in delivering a pathology reporting capability that is understandable and processable by computational means, allowing for new healthcare tools and processes to be developed and used safely.


The overall aims of the project are to-

  1. Understand current practice (specifically relating to PMIP messaging and PBCL)
  2. Investigate future requirements, and implementation options
  3. Propose a solution to deliver safe reliable communication of diagnostic results for both human (clinician) and computer interpretation, within the following constraints-
    1. Do not compromise (and if possible improve) usability and clarity for clinicians and patients
    2. Do not compromise (and if possible improve) patient safety
  4. Propose a migration path from the current state to the future solution

Workstream Structure

Stage Delivery Plan (provisional)

A more detailed plan of activities for the next stage of the UoM workstream has been defined. This is subject to approval and is provisional at this point.
UoM Stage Deliverables to 2021-03 v01

Current Status

NHS Digital has now published a table of Standard UCUM codes and Implementation Guidance in draft form for review and feedback. Please use the Review Feedback thread in the forum to access the documents and feed back any questions and review comments.

In August 2021 the Data Alliance Partnership Board (DAPB) published the Information Standard Notice DAPB4017: Pathology Test and Results Standard, which requires units of measure conforming to the Unified Code for Units of Measure (UCUM) standard to be used in pathology reporting whenever possible.

If you or a colleague have an interest in the subject of measurement and Units of Measure in pathology reporting, please look through the topics in the UoM Discussion Forum and UoM Design Issues forum in the first instance to get a feel of the kind of issues we are working on. Please feel free to contriobute to the forum discussions, or for more information contact me- colin.evans@nhs.net to discuss the goals of the projectand how you can contribute to our understanding of the requirements in this space.

Workstream Updates

Key Documents

Requirements & Solutions


  • Report on potential requirements vs. LSR and UCUM (NHS Digital Internal)
  • "e-Poster" presentation on the UK UoM project submitted for display at the SNOMED International Expo 2019 in Kuala Lumpur


For previous Done / Planned milestones please visit our Newsletter Archive.

Join the Conversation

The forum below is for general questions and discussion about the UoM project itself, and on the broader topic of Units of Measure in Pathology, including support in IT systems and related technologies including FHIR, SNOMED, UCUM and others.

To request access to site general forums please email pathologyandidagnostics@nhs.net

Tools and Resources


UCUM Validation and Conversion Tool at the US NLM

Web Service for UCUM (documentation page) at the US NLM

UCUM Essence browser (Excel)



Multiple Free Open-Source Software (FOSS) implementations of UCUM are available, plus other UCUM-related tools. Links to some established UCUM libraries are provided below for convenience, but please note inclusion here does not imply any level of approval or endorsement of a particular tool or library by NHS Digital.

lhncbc/ucum-lhc  (Javascript). This is the open source library that underpins the US NLM UCUM online service (listed above under Tools)

FHIR/Ucum-java (Java). Not a formal product of the HL7 organisation, but written and maintained by a key member of the HL7 FHIR community, and used (I understand) in multiple FHIR projects. There appears to be very little documentation for this implementation.

UoM User Reference Group (UoM URG)

The UoM URG is a group of group of stakeholders and subject matter experts that work with us to-

  • Understand clinical, technical and operational requirements
  • Assess available solutions and design options
  • Describe the requirements of stakeholder groups that will be affected by the decisions made
  • Make recommendations on how to address challenges

The Design Issues and Requirements areas, while open to all, are primarily for use by URG members to support the work of the group. If you would like to discuss joining the URG please contact me colin.evans@nhs.net

Collaborative Documents in Draft