The UMLS (Unified Medical Language System) is a set of files and software that brings together many health and biomedical vocabularies and standards (including several discussed in this training) to enable interoperability between computer systems. The UMLS integrates and distributes key terminology, classification and coding standards, and associated resources to promote creation of more effective and interoperable biomedical information systems and services, including electronic health records.

The UMLS includes the Metathesaurus, the Semantic Network, and the SPECIALIST Lexicon and Lexical Tools. The Metathesaurus is the largest component of the UMLS. It is a biomedical thesaurus that is organized by concept, or meaning, and it links similar names for the same concept from more than 180 different vocabularies. The Metathesaurus also identifies useful relationships between concepts and preserves the meanings, concept names, and relationships from each vocabulary.

The UMLS can be used to:

• Link terms and codes between your doctor, your pharmacy, and your insurance company.
• Coordinate patient care among several departments within a hospital.
• Process texts to extract concepts, relationships, or knowledge.
• Facilitate mapping between terminologies.
• Develop an information retrieval system.
• Extract specific terminologies from the Metathesaurus.
• Create and maintain a local terminology.
• Develop a terminology service.
• Research terminologies or ontologies.

The UMLS for Mapping

An important use of the UMLS is to build maps between different terminologies. The UMLS groups synonymous names into biomedical concepts and assigns a Concept Unique Identifier (CUI) to each distinct concept. Different terms from various terminologies that represent the same concept are linked to the same CUI.

Synonymy in the UMLS can be used to crosswalk between different vocabularies, aid in identifying meaning in text, and improve search and retrieval.

Accessing the UMLS

The UMLS can be accessed via the UMLS Terminology Services (UTS) website which gives you access to the UMLS downloads, browser, or application programming interface (API). To create a UTS account you must accept the terms of the UMLS Metathesaurus License. The UMLS License outlines restrictions regarding use and redistribution applicable to each source vocabulary. A full list of all source vocabularies in the UMLS can be found in the Vocabulary Documentation.