BYTETOOLS

MedlinePlus Genetics API

Free NIH MedlinePlus Genetics API with no key: plain-language summaries of genetic conditions, genes and chromosomes, written for patients and reviewed by experts. Tested example included.

No API key requiredHTTPSFree tier

Endpoint tested and returned HTTP 200 on 2026-08-21

What is the MedlinePlus Genetics API?

MedlinePlus Genetics is a free, key-free data service from the US National Library of Medicine. It provides expert-reviewed, plain-language summaries of genetic conditions, genes and chromosomes — covering causes, inheritance patterns, frequency and symptoms — as structured JSON files.

Most genetics APIs are built for researchers and return sequence identifiers, ontology codes and statistical associations. MedlinePlus Genetics is built for patients, and that is precisely what makes it valuable to anyone constructing a public-facing health application: the summaries are written in plain language, reviewed by genetics professionals, and carry the authority of the National Library of Medicine.

Distribution is unusually simple. Rather than a query API, each condition is a static JSON file addressed by its URL slug — the same slug used on the MedlinePlus website — served straight from the NIH's own host. That means no rate limits worth worrying about and trivially cacheable responses, but also no search: you need to know the slug in advance, which you get from the downloadable index of all conditions. The text fields contain HTML markup, and the record includes the reviewed date and full source citations.

Quick facts

Base URL
https://medlineplus.gov/download/genetics
Authentication
No API key or account. US federal government work in the public domain, though NIH asks that you do not imply endorsement.
Rate limit
No meaningful limit — these are static files on the NIH's host.
Pricing
Free. Public domain.
CORS
Not enabled — call it from your server
Official docs
Read the docs

How to use the MedlinePlus Genetics API

Every request below was executed against the live API on 2026-08-21, and the response shown is the real body it returned — not an illustration.

1. Fetch the summary for Alzheimer disease

GET https://medlineplus.gov/download/genetics/condition/alzheimer-disease.json

curl
curl 'https://medlineplus.gov/download/genetics/condition/alzheimer-disease.json'
JavaScript (fetch)
const res = await fetch("https://medlineplus.gov/download/genetics/condition/alzheimer-disease.json");
if (!res.ok) throw new Error(`Request failed: ${res.status}`);
const data = await res.json();
console.log(data);
Python (requests)
import requests

res = requests.get("https://medlineplus.gov/download/genetics/condition/alzheimer-disease.json", timeout=20)
res.raise_for_status()
print(res.json())
Response — HTTP 200 (truncated)
{
  "_comment": "See https://medlineplus.gov/about/data-files-api",
  "name": "Alzheimer disease",
  "ghr_page": "https://medlineplus.gov/genetics/condition/alzheimer-disease",
  "text-list": [
    {
      "text": {
        "html": "<p>Alzheimer disease is a degenerative disease of the brain that causes dementia, which is a gradual loss of memory, judgment, and ability to function. This disorder usually appears in people older than age 65, but less common forms of the disease appear earlier in adulthood.</p><p>Memory loss is the most common sign of Alzheimer disease. Forgetfulness may be subtle at first, but the loss of memory worsens over time until it interferes with most aspects of daily living. Even in familiar settings, a person with Alzheimer disease may get lost or become confused. Routine tasks such as preparing meals, doing laundry, and performing other household chores can be challenging. Additionally, it may become difficult to recognize people and name objects. Affected people increasingly require help with dressing, eating, and personal care.</p><p>As the disorder progresses, some people with Alzheimer disease experience personality and behavioral changes and have trouble interacting in a socially appropriate manner. Other common symptoms include agitation, restlessness, withdrawal, and loss of language skills. People with this disease usually require total care during the advanced stages of the disease.</p><p>Affected individuals usually survive 8 to 10 years after the appearance of symptoms, but the course of the disease can range from 1 to 25 years. Survival

Parameters

ParameterTypeRequiredDescription
typepath segmentRequired`condition`, `gene` or `chromosome`. condition
slugpath segmentRequiredThe condition, gene or chromosome slug with `.json` appended — the same slug used in the MedlinePlus web URL. alzheimer-disease.json
(index)path segmentOptionalA downloadable index file lists every available slug, which is how you discover them since there is no search endpoint.

Response fields

namestring
The condition, gene or chromosome name.
ghr_pagestring
Canonical MedlinePlus page URL for the record — use it for attribution and to link readers to the source.
text-listarray
The substantive content, as sections covering description, causes, inheritance, frequency and related information.
text-list[].text.htmlstring
Section body as HTML. Sanitise before rendering, and do not assume plain text.
synonymsarray
Alternative names the condition is known by, useful for search matching.
related-gene-listarray
Genes associated with the condition, linking into the gene records.
reviewedstring
Date the entry was last reviewed by NIH staff — display it, since medical content ages.
(references)array
Source citations, typically to PubMed.

What you can build with the MedlinePlus Genetics API

  • Add plain-language condition explanations to a patient portal
  • Build a genetics education or public health resource
  • Provide accessible context alongside technical genomic results
  • Cross-reference condition names to associated genes

Common errors and how to fix them

404

The slug does not exist.

Fix: There is no search endpoint. Fetch the index file to get the exact slug — it matches the MedlinePlus web URL, hyphenated and lowercase.

HTML inside text fields

Not an error — content is stored as HTML.

Fix: Sanitise before rendering. Stripping tags naively will lose paragraph structure and emphasis.

Content seems dated

Entries are reviewed periodically, not continuously.

Fix: Read and display the `reviewed` date. Presenting medical content without its review date is misleading.

MedlinePlus Genetics API — frequently asked questions

Is the MedlinePlus Genetics API free?

Yes, free with no API key or account. It is US federal government work in the public domain, though the NIH asks that you do not present your use as an endorsement.

How is this different from other genetics APIs?

It is written for patients rather than researchers. Where UniProt or Ensembl return sequence data and identifiers, MedlinePlus returns expert-reviewed plain-language explanations of what a condition is, what causes it and how it is inherited.

How do I search for a condition?

You cannot search through the API — each record is a static JSON file addressed by slug. Download the index file listing every available slug, cache it, and search that locally.

Can I use this content on my own health site?

Yes, it is public domain. Display the `reviewed` date alongside it and link back to the canonical MedlinePlus page, since medical content ages and readers deserve to see the source and its currency.

Tools that pair with this API

MedlinePlus Genetics is an independent third-party service and is not affiliated with ByteTools or ByteVancer. Details on this page were verified on 2026-08-21; always check the official documentation before relying on this API in production, as terms and limits can change.