Introducing the Unified Medical Language System (UMLS): 

NLM’s framing structure for clinical practice and life sciences

Laël Cranmer Gatewood, PhD

Health Informatics

University of Minnesota, USA

Since 1879, the U.S. National Library of Medicine (NLM) has provided reference materials for researchers and clinicians in biology and medicine. Best known for its Medline/PubMed indexing and retrieval services, NLM has initiated many other types of informatics projects to support practice, research, teaching and assessment. With the evolution of coding systems such as ICD, SNOMED and HL7, NLM developed a comprehensive approach known as the Unified Medical Language System, to frame many knowledge bases for medicine and nursing. The UMLS gathers together a Metathesaurus, a Semantic Network and a SPECIALIST Lexicon to map over 60 vocabularies, in many different languages. Applications include search programs for the National Institutes of Health (NIH), definitions needed for U.S. private health information, and detailed relationships for health information exchange.