MedlinePlus Connect API

National Library of Medicine · Health

Health No Auth Free & Open Healthcare Patient Education ICD-10 RxNorm

NLM MedlinePlus Connect links clinical code sets (ICD-10-CM, RxNorm, LOINC, SNOMED CT) to patient-friendly health topic content. Designed for EHR integration to surface patient education materials at the point of care.

Authentication

No authentication requiredFree to use with no key needed.

Sample Requests

GET Get health topics for ICD-10 code

Get patient health topic links for an ICD-10-CM diagnosis code

https://connect.medlineplus.gov/service?knowledgeResponseType=application/json&mainSearchCriteria.v.c=E11.9&mainSearchCriteria.v.cs=2.16.840.1.113883.6.90

Hover any highlighted part to learn what it does

curl -X GET "https://connect.medlineplus.gov/service?knowledgeResponseType=application%2Fjson&mainSearchCriteria.v.c=E11.9&mainSearchCriteria.v.cs=2.16.840.1.113883.6.90"

import requests
params = {
    "knowledgeResponseType": "application/json",
    "mainSearchCriteria.v.c": "E11.9",
    "mainSearchCriteria.v.cs": "2.16.840.1.113883.6.90"
}
response = requests.get(
    "https://connect.medlineplus.gov/service",
    params=params,
)
print(response.json())

const url = new URL('https://connect.medlineplus.gov/service');
url.searchParams.set('knowledgeResponseType', 'application/json');
url.searchParams.set('mainSearchCriteria.v.c', 'E11.9');
url.searchParams.set('mainSearchCriteria.v.cs', '2.16.840.1.113883.6.90');

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://connect.medlineplus.gov/service")
	q := baseURL.Query()
	q.Set("knowledgeResponseType", "application/json")
	q.Set("mainSearchCriteria.v.c", "E11.9")
	q.Set("mainSearchCriteria.v.cs", "2.16.840.1.113883.6.90")
	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://connect.medlineplus.gov/service")
uri.query = URI.encode_www_form({
  "knowledgeResponseType" => "application/json",
  "mainSearchCriteria.v.c" => "E11.9",
  "mainSearchCriteria.v.cs" => "2.16.840.1.113883.6.90"
})

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://connect.medlineplus.gov/service?" . http_build_query([
    "knowledgeResponseType" => "application/json",
    "mainSearchCriteria.v.c" => "E11.9",
    "mainSearchCriteria.v.cs" => "2.16.840.1.113883.6.90"
]);
$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

Get Postman ↗

No API key required — public NIH service
In Postman, GET https://connect.medlineplus.gov/service
Add params: mainSearchCriteria.v.c={ICD10 code} and mainSearchCriteria.v.cs=2.16.840.1.113883.6.90
Add knowledgeResponseType=application/json for JSON response
Response returns links to patient-readable health topics for the diagnosis code

What can you build with MedlinePlus Connect API?

MedlinePlus Connect 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

No authentication required. This API is open — no signup or key needed. Ideal for quick prototypes and public-facing features. MedlinePlus Connect 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?

Open documentation ↗