umls

is an Aggregator.

The Unified Medical Language System (UMLS) integrates and distributes over 200 biomedical vocabularies, terminologies, and classification standards to enable interoperability between information systems. It includes the Metathesaurus (terms and codes from vocabularies like CPT, ICD-10-CM, LOINC, MeSH, RxNorm, SNOMED CT), Semantic Network (broad categories and relationships), and SPECIALIST Lexicon (biomedical and general English lexicon with normalization tools).

Domains

biomedical, clinical, literature

License

UMLS License (free for individuals)

Homepage

umls

Repository

Unknown

Infores ID

infores:umls

FAIRsharing ID

Unknown

Product Summary

Products

From this Resource
ID Name URL Category Format Description
umls.browser UMLS Metathesaurus Browser home GraphicalInterface http Web interface for browsing UMLS Metat...
umls.semantic_network_browser UMLS Semantic Network Browser root GraphicalInterface http Web interface for viewing semantic ty...
umls.api UMLS Terminology Services API home.html ProgrammingInterface ❔ REST API providing programmatic acces...
umls.release UMLS Knowledge Sources Release Files umlsknowledgesources.html Product ❔ Full UMLS Knowledge Sources release i...
umls.metamorphosys MetamorphoSys Customization Tool help.html ProcessProduct ❔ MetamorphoSys tool for customizing UM...
umls.specialist_lexicon SPECIALIST Lexicon and Lexical Tools index.html ProcessProduct ❔ SPECIALIST Lexicon and Lexical Tools ...
ndfrt.umls VANDF in UMLS umls Product ❔ VANDF drug terminology data distribut...
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medgen.mgconso MGCONSO (Concept Names) MGCONSO.RRF.gz (15.1 MB) Product txt Rich Release Format (RRF) file contai...
medgen.mgdef MGDEF (Definitions) MGDEF.RRF.gz (4.8 MB) Product txt Rich Release Format (RRF) file contai...
medgen.mgrel MGREL (Relationships) MGREL.RRF.gz (14.9 MB) MappingProduct txt Rich Release Format (RRF) file contai...
medgen.mgsat MGSAT (Attributes) MGSAT.RRF.gz (11.2 MB) Product txt Rich Release Format (RRF) file contai...
medgen.mgsty MGSTY (Semantic Types) MGSTY.RRF.gz (1.6 MB) Product txt Rich Release Format (RRF) file contai...
medgen.names NAMES NAMES.RRF.gz (3.0 MB) Product txt Rich Release Format (RRF) file contai...
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Details

Unified Medical Language System (UMLS)

Overview

The Unified Medical Language System (UMLS) is a comprehensive set of files and software developed by the U.S. National Library of Medicine (NLM) that brings together over 200 health and biomedical vocabularies and standards to facilitate interoperability between computer systems. The UMLS enables linking of different medical terminologies and codes used by physicians, pharmacies, insurance companies, hospitals, and research institutions.

Three Knowledge Sources

1. Metathesaurus

The Metathesaurus is the largest component, containing:

  • Terms and codes from many vocabularies including:
    • CPT (Current Procedural Terminology)
    • ICD-10-CM (International Classification of Diseases)
    • LOINC (Logical Observation Identifiers Names and Codes)
    • MeSH (Medical Subject Headings)
    • RxNorm (normalized drug names)
    • SNOMED CT (Systematized Nomenclature of Medicine Clinical Terms)
  • Hierarchical relationships
  • Definitions and other attributes
  • Concept Unique Identifiers (CUIs) linking synonymous terms across vocabularies

2. Semantic Network

Provides a consistent categorization of all concepts represented in the Metathesaurus through:

  • 133 broad categories (semantic types) such as “Disease or Syndrome,” “Pharmacologic Substance”
  • 54 relationships (semantic relations) defining interactions between semantic types

3. SPECIALIST Lexicon and Lexical Tools

  • Large syntactic lexicon covering biomedical and general English
  • Tools for normalizing strings, generating lexical variants, and creating indexes
  • Supports natural language processing of biomedical text

Use Cases

The UMLS can be used to:

  • Link terminology between healthcare providers, pharmacies, and insurance companies
  • Coordinate patient care across hospital departments
  • Process clinical texts to extract concepts and relationships
  • Map between different terminologies
  • Develop information retrieval systems
  • Extract custom terminologies from the Metathesaurus
  • Build and maintain local terminology services
  • Research terminologies and ontologies

Access Methods

Web Browsers

  • Metathesaurus Browser for searching concepts and relationships
  • Semantic Network Browser for exploring semantic types and relations

Local Installation

  • Download full UMLS release files
  • Customize using MetamorphoSys tool
  • Load into local database systems (MySQL, Oracle, etc.)

Programmatic Access

  • REST API for querying UMLS data within applications
  • Comprehensive API documentation available

Licensing

  • Free licensing for individuals (not groups or organizations)
  • UMLS Terminology Services (UTS) account required
  • No charge for SNOMED CT use in United States and member countries
  • Some vocabularies may require additional agreements with vendors

Maintained By

National Library of Medicine, National Institutes of Health, U.S. Department of Health and Human Services

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Created: October 30, 2025 | Last modified: October 30, 2025