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Check out the Postman sample collection to help you get started using the UMLS REST API.

API Terms of Service

Retrieving UMLS Concept Definitions

URIs | Query Parameters | Sample Output

URIs with /definitions support the following use cases:

Note that ‘current’ in the URI can always be used to search against the latest UMLS publication.
You may use any valid UMLS release back to 2008AA in your URI if you would like to search against a particular version of the UMLS.


The base URI is

Sample URI Description Returned JSON Object classType
/content/current/CUI/C0155502/definitions Retrieves definitions of the CUI Definition

Query Parameters

Parameter name Required? Y/N Description Valid Values Default value Usage Note
apiKey Y An API key is required for each call to the API. Visit your UTS profile to obtain your API key. n/a n/a n/a
sabs N Comma-separated list of source vocabularies to include in your search Any root source abbreviation in the UMLS. See the “Abbreviation” column for a list of UMLS source vocabulary abbreviations. All UMLS source vocabularies Use a comma between each source abbreviation to specify more than one.
pageNumber N Whole number that specifies which page of results to fetch. 1,2,3, etc 1 n/a
pageSize N Whole number that specifies the number of results to include per page. 1,2,3, etc 25 n/a

Sample Output

Sample output for…

    "pageSize": 25,
    "pageNumber": 1,
    "pageCount": 1,
    "result": [
            "classType": "Definition",
            "sourceOriginated": true,
            "rootSource": "MSH",
            "value": "Idiopathic recurrent VERTIGO associated with POSITIONAL NYSTAGMUS. It is associated with a vestibular loss without other neurological or auditory signs. Unlike in LABYRINTHITIS and VESTIBULAR NEURONITIS inflammation in the ear is not observed."