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SNOMEDCT_US (SNOMED CT, US Edition) - Synopsis

Search SNOMEDCT_US in the UMLS Metathesaurus
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The U.S. National Library of Medicine (NLM) produces the US Edition of SNOMED CT.

The Systematized Nomenclature of Medicine-Clinical Terms (SNOMED CT®) was originally created by the College of American Pathologists by combining SNOMED RT and Clinical Terms Version 3. SNOMED CT intellectual property rights were transferred to the SNOMED Standards Development Organisation (SDO) in the formal creation of the IHTSDO (International Health Terminology SDO).

SNOMED CT aims to improve patient care through the development of systems to record health care encounters accurately.

The US Edition of SNOMED CT facilitates 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 in the US.

The US Edition of SNOMED CT combines the International Release of SNOMED CT and the US Extension of SNOMED CT

SNOMED CT provides the core general terminology for the electronic health record (EHR). The concepts have unique meanings and formal logic-based definitions organized into hierarchies. Each International Release includes the core of the terminology (concepts, descriptions, and relationships), together with works to support the implementation and use of SNOMED CT, including subsets, cross maps to existing classifications and coding schemes, and an extensive set of guidelines.

The US Extension to SNOMED CT included the concepts, descriptions, and relationships accepted by NLM as a formal extension to the SNOMED CT International Release. NLM no longer releases the standalone US Extension.

The US Edition of SNOMED CT includes more than 300,000 unique concepts. There are over 1,000,000 descriptions in SNOMED CT, including synonyms that can be used to refer to a concept. In addition, there are approximately 903,000 links or semantic relationships between the SNOMED CT concepts.

UMLS licensees may download the US Edition release and International Release files.

As of 2013AB, the Metathesaurus includes the US Edition and no longer includes the separate International Release and US Extension.

SNOMED CT is used by standards setting organizations and in a variety of health care applications. It is also utilized by developers of electronic health data exchange applications.

Update Frequency
The US Edition is updated in March and September, approximately one month after each new International Release.

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

Sites Consulted

  1. International Health Terminology Standards Development Organisation [Internet]. Copenhagen: International Health Terminology Standards Development Organisation. SNOMED CT; [cited 2008 Sep 17]. Available from:; About SNOMED CT:; SNOMED CT components:; Release of SNOMED CT:
  2. US Edition of SNOMED CT® [Internet]. Bethesda (MD): National Library of Medicine (US); 2013 May 16 [reviewed 2014 Mar 03; updated 2014 Mar 03; cited 2014 Apr 16]. Available from:
  3. 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: