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National Library of Medicine Technical BulletinNational Library of Medicine Technical Bulletin

Table of Contents: 2020 MAY–JUNE No. 434

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UMLS® 2020AA Release Available

Wilder V. UMLS® 2020AA Release Available. NLM Tech Bull. 2020 May-Jun;(434):e1

2020 May 05 [posted]

The 2020AA release of the Unified Medical Language System® (UMLS) Knowledge Sources is available for download as of May 4, 2020.

The available downloads are:

  • Full Release (UMLS Metathesaurus, Semantic Network, Specialist Lexicon and Lexical Tools, database load scripts, and MetamorphoSys for customizing your UMLS subset and browsing the data)
  • UMLS Metathesaurus Files (complete Metathesaurus data without any customization)
  • MRCONSO.RRF file (most widely used Metathesaurus file)

The UMLS SOAP API is deprecated as of the 2020AA release. The SOAP API will be discontinued on December 31, 2020. SOAP API users are encouraged to switch to the REST API.


The 2020AA Metathesaurus contains approximately 4.28 million concepts and 15.5 million unique concept names from 214 source vocabularies.

Two new sources:

  • CCSR_10 (Clinical Classifications Software Refined for ICD-10-CM)
  • LNC_SPECIAL_USE (Logical Observation Identifier Names and Codes (LOINC), Prerelease Terms, Special Use). This source includes coronavirus-related special use codes available as of March 13, 2020.

One new MedDRA translation:
  • MDRKOR (Korean Edition of the Medical Dictionary for Regulatory Activities Terminology (MedDRA))

One new NCI sub-source:

  • NCI_BRIDG_3_0_3 (Biomedical Research Integrated Domain Group Model)

MTHHH update:

  • The Metathesaurus no longer includes MTHHH (Metathesaurus HCPCS Hierarchical Terms) and its associated TTY = HT. The HCPCS hierarchy is now represented by SAB = HCPCS and TTY = MTH_HT.

68 English sources and 38 translation sources were updated. These include MeSH®, MedDRA, RxNorm, and SNOMED CT® (English and Spanish). A complete list is available in the Updated Sources section of the Release Documentation. For more detailed information on changes in this version of the Metathesaurus, see the Updated Sources (Expanded) section. Additional release statistics may be found in the Statistics section.

SPECIALIST Lexicon and Lexical Tools

  • The release includes the updated SPECIALIST Lexicon (2020 Release).
  • The release includes the updated Lexical Tools (2020 Release) which integrate data from the SPECIALIST Lexicon, 2020 Release. The Lexical Tools include the Full and Lite versions of lvg.2020.
  • The Metathesaurus index files were processed using the updated lvg files.
  • The updated SPECIALIST Lexicon and Lexical Tools feature synonym enhancements that include changes to their file structure. See the SPECIALIST Lexicon and Lexical Tools web sites for details about these file changes and other updates.


  • The full release requires 32.1 GB of disk space.

Reported bugs may be viewed on the Release Notes and Bugs web page.

MetamorphoSys can generate custom load scripts for MySQL, Oracle, or Microsoft Access when creating a Metathesaurus subset or installing the Semantic Network. Instructions are available on the UMLS Load Scripts homepage.

Release Information

To access the UMLS Release files, you must have an active UMLS Metathesaurus® License and a valid UTS account. You will be prompted for your UTS username and password when downloading the files.

UMLS Learning Resources

2020AA Source Release Documentation web pages are available.

Additional information regarding the UMLS is available on the UMLS homepage. New users are encouraged to take the UMLS Basics Tutorial and to explore the UMLS Quick Start Guide, and other training materials.

UMLS Terminology Services (UTS)

The UTS Metathesaurus Browser and the UTS SOAP API and REST API include the updated release.

In addition, the UTS SNOMED CT Browser now features the March 2020 US Edition of SNOMED CT.

UMLS User Contributions

UMLS users have extended the functionality of the UMLS in a variety of ways by developing APIs, automation scripts, and natural language processing tools. You can find a list of these on the UMLS Community web page.

Want to add your tool? Send a request to NLM Customer Support with the subject line: "UMLS Community."

Be sure to include a link to your source code so that other UMLS users can adapt your tool. We are especially interested in:

  • Database load scripts
  • Transformation scripts that convert UMLS data into other formats (for example, RDF or JSON)
  • Scripts that automate any aspect of UMLS installation
  • Applications that leverage UMLS in the processing of text

By Victoria Wilder
MEDLARS Management Section

NLM Technical Bulletin National Library of Medicine National Institutes of Health