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Unified Medical Language System® (UMLS®)

2012AB US Extension to SNOMED CT Source Information

Web site:

The U.S. National Library of Medicine (NLM) produces the US Extension to SNOMED CT.

The US Extension to SNOMED CT faciliates the use of SNOMED CT as a primary coding terminology for clinical information in electronic health records, research and clinical trials. It is used with RxNorm and LOINC to cover medications and laboratory tests needs.

The US Extension to SNOMED CT lists the concepts, descriptions, and relationships accepted by NLM as a formal extension to the SNOMED CT International Release.

UMLS licensees may download the US Extension release files.

For more information about SNOMED CT in the Metathesaurus, see the SNOMED CT source synopsis.

Update Frequency
The US Extension is updated in March and August, one month after each new SNOMED CT International Release.

Metathesaurus Update Frequency
The US Extension is an updated source in each Metathesaurus release.

Sites Consulted

  1. US Extension to SNOMED CT® [Internet]. Bethesda (MD): National Library of Medicine (US); 2011 Mar 22 [reviewed 2012 May 15; updated 2012 May 15; cited 2012 June 12]. Available from: