What is the UMLS?

The Unified Medical Language System, or UMLS, is a project run by the National Library of Medicine that aggregates many of the common knowledge bases used in medicine. It provides a unique set of identifiers for the concepts in these terminologies in an attempt to create a unified view of the disparate medical knowledge bases.

For example, two of the common knowledge bases used in medicine are RxNorm, which captures knowledge about drugs, and SNOMED CT, which is a general-use medical knowledge base. Both knowledge bases contain concepts used to represent the drug naproxen.

In SNOMED CT, the concept representing naproxen has an id 11847009. In RxNorm, the id for naproxen is 7258. The UMLS creates a unified view of these two individual representations of naproxen by connecting the RxNorm and SNOMED CT ids with something call a CUI, or Concept Unique Identifier. The CUI for naproxen is C0027396.

What is a CUI?

A CUI, or Concept Unique Identifier, is an id assigned by the National Library of Medicine’s Unified Medical Language System project. CUIs are intended to connect together the same concept when they exist in two different knowledge bases.