UMLS REST API
National Library of Medicine · Health
Unified Medical Language System (UMLS) REST API from NIH/NLM. Cross-vocabulary concept lookups spanning ICD-10, SNOMED CT, LOINC, RxNorm, CPT, and 200+ biomedical vocabularies. Essential for medical terminology mapping and interoperability.
Authentication
Sample Requests
Search across all UMLS vocabularies for a medical concept
Hover any highlighted part to learn what it does
curl -X GET "https://uts-ws.nlm.nih.gov/rest?apiKey=%7Byour_api_key%7D&string=diabetes%20mellitus&searchType=words"
import requests
params = {
"apiKey": "{your_api_key}",
"string": "diabetes mellitus",
"searchType": "words"
}
response = requests.get(
"https://uts-ws.nlm.nih.gov/rest",
params=params,
)
print(response.json())const url = new URL('https://uts-ws.nlm.nih.gov/rest');
url.searchParams.set('apiKey', '{your_api_key}');
url.searchParams.set('string', 'diabetes mellitus');
url.searchParams.set('searchType', 'words');
const response = await fetch(url);
const data = await response.json();
console.log(data);package main
import (
"fmt"
"io"
"net/http"
"net/url"
)
func main() {
baseURL, _ := url.Parse("https://uts-ws.nlm.nih.gov/rest")
q := baseURL.Query()
q.Set("apiKey", "{your_api_key}")
q.Set("string", "diabetes mellitus")
q.Set("searchType", "words")
baseURL.RawQuery = q.Encode()
targetURL := baseURL.String()
req, _ := http.NewRequest("GET", targetURL, nil)
client := &http.Client{}
resp, _ := client.Do(req)
defer resp.Body.Close()
body, _ := io.ReadAll(resp.Body)
fmt.Println(string(body))
}require "net/http"
require "json"
uri = URI("https://uts-ws.nlm.nih.gov/rest")
uri.query = URI.encode_www_form({
"apiKey" => "{your_api_key}",
"string" => "diabetes mellitus",
"searchType" => "words"
})
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = uri.scheme == "https"
req = Net::HTTP::Get.new(uri)
res = http.request(req)
puts JSON.parse(res.body)<?php
$url = "https://uts-ws.nlm.nih.gov/rest?" . http_build_query([
"apiKey" => "{your_api_key}",
"string" => "diabetes mellitus",
"searchType" => "words"
]);
$opts = ["http" => [
"method" => "GET",
]];
$ctx = stream_context_create($opts);
$res = file_get_contents($url, false, $ctx);
print_r(json_decode($res, true));Postman Setup Guide
- Register free at https://uts.nlm.nih.gov/uts/signup-login for a UMLS license and API key
- In Postman, GET https://uts-ws.nlm.nih.gov/rest/search/current
- Add params: string={term}, apiKey={your_key}, searchType=words
- Results return CUI (concept identifier) and source vocabularies
- Use CUI to fetch concept details: GET /rest/content/current/CUI/{cui}
What can you build with UMLS REST API?
UMLS REST API is a Health API. Developers commonly use health APIs for:
- accessing medical reference data and drug information
- building patient-facing health tracking apps
- integrating with EHR and telemedicine platforms
- looking up ICD codes and clinical terminology
- powering wellness and fitness applications
API Key authentication. You'll receive a key after signing up. Send it with every request — in a header or query parameter. Keep it out of client-side code and never commit it to version control. UMLS REST API is free to use, making it a low-risk choice to experiment with.
New to APIs? Read our beginner's guide · Learn about API keys · What is REST?