ClinicalTrials.gov API

clinicaltrials.gov · Health

Health No Auth Free & Open Healthcare Clinical Trials Research

US National Library of Medicine database of clinical studies — 500,000+ studies worldwide. Search by condition, drug, location, status, and more. Free, no API key.

Authentication

No authentication requiredFree to use with no key needed.

Sample Requests

GET Search studies

Find clinical trials on COVID-19 vaccines.

https://clinicaltrials.gov/api/v2/studies?format=json&pageSize=5&query.cond=COVID-19&query.intr=vaccine

Hover any highlighted part to learn what it does

curl -X GET "https://clinicaltrials.gov/api/v2/studies?format=json&pageSize=5&query.cond=COVID-19&query.intr=vaccine"

import requests
params = {
    "format": "json",
    "pageSize": "5",
    "query.cond": "COVID-19",
    "query.intr": "vaccine"
}
response = requests.get(
    "https://clinicaltrials.gov/api/v2/studies",
    params=params,
)
print(response.json())

const url = new URL('https://clinicaltrials.gov/api/v2/studies');
url.searchParams.set('format', 'json');
url.searchParams.set('pageSize', '5');
url.searchParams.set('query.cond', 'COVID-19');
url.searchParams.set('query.intr', 'vaccine');

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://clinicaltrials.gov/api/v2/studies")
	q := baseURL.Query()
	q.Set("format", "json")
	q.Set("pageSize", "5")
	q.Set("query.cond", "COVID-19")
	q.Set("query.intr", "vaccine")
	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://clinicaltrials.gov/api/v2/studies")
uri.query = URI.encode_www_form({
  "format" => "json",
  "pageSize" => "5",
  "query.cond" => "COVID-19",
  "query.intr" => "vaccine"
})

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://clinicaltrials.gov/api/v2/studies?" . http_build_query([
    "format" => "json",
    "pageSize" => "5",
    "query.cond" => "COVID-19",
    "query.intr" => "vaccine"
]);
$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 needed
Search: GET /api/v2/studies?query.cond=cancer&pageSize=10&format=json
Filter by status: &filter.overallStatus=RECRUITING
Near location: &query.locn=New+York
Single study: GET /api/v2/studies/{NCT_ID}?format=json

What can you build with ClinicalTrials.gov API?

ClinicalTrials.gov 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. ClinicalTrials.gov API is free to use, making it a low-risk choice to experiment with.

New to APIs? Read our beginner's guide

Open documentation ↗