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Unified Medical Language System® (UMLS®)

2024AA UMLS® Release Notes and Bugs

What's New

The 2024AA release of the Unified Medical Language System® (UMLS) Knowledge Sources is available for download as of May 6, 2024.

The available downloads are:

UMLS Metathesaurus Precomputed Subsets

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

UMLS Metathesaurus History Files

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 2024AA Metathesaurus contains approximately 3.38 million concepts and 16.4 million unique concept names from 187 source vocabularies.

Two new translations:

33 English sources and 46 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.

SPECIALIST Lexicon and Lexical Tools

The Metathesaurus index files were processed using the updated lvg files.


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

2024AA 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 other training materials.

UMLS Terminology Services (UTS)

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


New Terminology Release API Endpoint

This endpoint provides an updated list of releases for RxNorm, SNOMED CT, and UMLS. You can use this endpoint to completely automate the retrieval of the latest release files without having to manually download the files. For example, if you load RxNorm data weekly or monthly, you can monitor our release API and automatically download the data immediately when it becomes available.



Request all RxNorm Full Monthly Releases:


Request the current RxNorm Full Monthly Release:


"fileName": "",

"releaseVersion": "2024-01-02",

"releaseDate": "2024-01-02",


"releaseType": "RxNorm Full Monthly Release",

"product": "RxNorm",

"current": true



Download the current RxNorm Full Monthly Release:

curl "https://uts-

zip&apiKey=YOUR_API_KEY" -o

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:

We value your feedback! For more information about improvements we have made to the UMLS based on user feedback, as well as information about UMLS use in general, see our UMLS User Feedback Page:

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 this 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: May 6, 2024