Introducing the LOINC Ontology: A LOINC and SNOMED CT Interoperability Solution

ABOUT The LOINC Ontology supports providers and users who implement different combinations of SNOMED CT and LOINC in health information systems and allows them to meet clinical and regulatory requirements in a single solution. An extension of SNOMED CT’s ontological framework, the ontology creates SNOMED CT and LOINC codes for all concepts that are shared between the terminologies. SNOMED CT provides the computable framework and LOINC provides laboratory and pathology content in an understood format to countries that do not currently use LOINC.

VERSION 2.82 MARCH 2026 This third production release of the LOINC Ontology changes its versioning to reflect the LOINC version from which it is sourced. The new version includes more than 45,000 concepts, including 78% of the top 20,000 most used LOINC concepts.

WEBSITE NOTICE In the near future, the website home for this project will move to loinc.org/ontology to ease maintenance and support.

RESOURCES

• Technical Release Notes for v2.82
• Implementation Guide
• Frequently Asked Questions
• Version 1.0 Webinar Video

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BACKGROUND A new cooperative agreement was signed between the Regenstrief Institute (RII) and SNOMED International (IHTSDO) in 2022 and renewed in 2025. The organizations agreed to work together to minimize duplication between LOINC and SNOMED CT and to enhance the ability of stakeholders to use the two terminologies together. A primary aim of the agreement is to create an extension of SNOMED CT for the LOINC terminology. This effort builds on strengths of both terminologies by increasing the computability of LOINC and making the more granular observables in LOINC available to be used in a SNOMED format integrated with SNOMED CT concepts.