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2022AB UMLS® Release Notes and Bugs

What's New

The 2022AB release of the Unified Medical Language System® (UMLS) Knowledge Sources is available for download as of November 7, 2022.

The available downloads are:
  • NEW: UMLS Metathesaurus Precomputed Subsets (Requires no installation, see below for more information.)
  • RRF file (Most widely used Metathesaurus file.)
  • 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.)
  • NEW: UMLS Metathesaurus History Files (Files that contain historical data from the UMLS Metathesaurus.)

NEW: UMLS Metathesaurus Precomputed Subsets

In past years, we have required the use of MetamorphoSys to install and customize the UMLS Metathesaurus. For the 2022AB release, we are providing two ready-to-use precomputed subsets of the UMLS Metathesaurus that require no installation or customization.

  • UMLS Metathesaurus Full Subset (complete Metathesaurus data without any customization)
  • UMLS Metathesaurus Level 0 Subset (Includes only level 0 source vocabularies. Level 0 vocabularies do not have any additional restrictions beyond the standard license terms)
We are considering a new approach to generating UMLS subsets, and we would like your feedback. The new approach may involve producing new precomputed subsets or configuring subsets in a web browser instead of in MetamorphoSys. We are interested in knowing which features of MetamorphoSys our users consider essential. Please submit your comments to the NLM Help Desk ( using the subject line: 'UMLS Subsets”

NEW: UMLS Metathesaurus History Files

We are pleased to announce the addition of three new files that contain historical data from the UMLS Metathesaurus.

  • Concept History (MRCONSO_HISTORY.txt) - This file contains all atoms, concepts, and codes that were dropped from the UMLS Metathesaurus MRCONSO.RRF starting with the 2004AA release.
  • Relation History (MRREL_HISTORY.txt) - This file contains all relations dropped from the UMLS Metathesaurus MRREL.RRF file starting with the 2004AA release.
  • Source Vocabulary History (MRSAB_HISTORY.txt) - This file includes a row for every version of every UMLS source vocabulary updated in the UMLS Metathesaurus MRSAB.RRF file starting with the 2004AA release.
These files are available from the UMLS Download page:

Please let us know if you find these files useful with comments to the NLM Help Desk ( using the subject line: 'UMLS History Files”.


The 2022AB Metathesaurus contains approximately 4.66 million concepts and 17.2 million unique concept names from 182 source vocabularies.

One new source: 
- ORPHANET (Orphanet Nomenclature)

Three new translations:
- LNC-UK-UA (LOINC Linguistic Variant - Ukrainian, Ukraine)
- MDRLAV (Latvian Edition of the Medical Dictionary for Regulatory Activities Terminology (MedDRA))
- MDRSWE (Swedish Edition of the Medical Dictionary for Regulatory Activities Terminology (MedDRA))

NCI subsources update: 
- The  representation of the NCI Thesaurus in the UMLS has changed. We are retaining all content with the 'NCI'Thesaurus source abbreviation, but we removed content from all NCI Thesaurus sub-sources. Users interested in the codes and names from the NCI Thesaurus sub-sources can still find them in the NCI Metathesaurus (
31 English sources and 34 translation sources were updated. These include MeSH®, MedDRA, RxNorm, and SNOMED CT® (English and Spanish).  For 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.


  • The full release requires 34.6 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 to authenticate with an identity provider with the UTS when downloading the files.

UMLS Learning Resources
2022AB Source Release Documentation Web pages are available.

Additional information regarding the UMLS is available on the UMLS homepage. New users are encouraged to 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 REST API include the updated release.


We have made a new API endpoint available for automating downloads of RxNorm, SNOMED CT, and UMLS release files. Simply provide the URL and your API key. For example:
curl example:
curl "" -o
For more information, see:


UMLS REST API authentication has changed. You can now authenticate by simply appending an apiKey parameter to your request, for example:{{YOUR_API_KEY}}.  

Authentication via ticket-granting tickets (TGTs) and service tickets is deprecated, but we will continue to accept API authentication via this method until the end of 2023. 

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 the NLM Help Desk ( 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

For information on the Unified Medical Language System (UMLS), consult the UMLS homepage at:

The latest Release Notes list all known issues, including bugs and fixes, and are available at:

UMLS data files and MetamorphoSys are available by download from the UMLS Web site at: Users must have an active UMLS Terminology Services (UTS) account to download the files. All files must be downloaded into the same directory.  MetamorphoSys must be unzipped before it can be used.


There are no known problems for the 2022AB release. 

Please send any issues or concerns to NLM Customer Service.

UMLS Problems (Bugs) for Previous Versions

Release information for the RRF Browser

Last Reviewed: November 6, 2022