The MSD Manuals — known as the Merck Manuals in the United States and Canada — are a medical reference published by Merck & Co., Inc. (Rahway, NJ, USA; called MSD elsewhere) and first published in 1899. Today the manuals are free on the web and as mobile apps. They come in two reader editions: a Professional Version for clinicians and a Consumer Version that rewrites the same medical content in plain language for patients and families who want to look up diseases, symptoms, tests, and treatments. An official Simplified Chinese edition is operated at msdmanuals.cn, alongside the global site msdmanuals.com.
At a Glance
- URL: msdmanuals.com (global); msdmanuals.cn (official Chinese edition)
- Type: Online medical reference (encyclopedic)
- Cost: Completely free, no advertising
- Registration: None required; the publisher states it does not collect users' personal data
- Languages: 16 languages as of 2026-09-01, including English, Chinese, Japanese, Korean, French, German, Spanish, Russian, and Arabic
Background
The manual began in 1899 as Merck's Manual of the Materia Medica, a small reference book for physicians and pharmacists, and grew into one of the most widely used comprehensive medical resources for professionals and consumers. It is branded Merck Manual in the US and Canada and MSD Manual elsewhere; page footers credit Merck & Co., Inc., Rahway, NJ, USA and its affiliates.
The publisher frames the manuals as a public good: its mission statement holds that "health information is a universal right," so the digital editions are free for professionals and patients. Since 2015, the Global Medical Knowledge initiative has aimed to make the manuals available to up to 3 billion people worldwide, with all translations published online and kept current. The Chinese site, msdmanuals.cn, states in its footer that it is a non-profit site operated by MSD China.
Consumer and Professional Versions
The same handbook ships in two reader editions, switchable from the page header:
- Consumer Version (
/home): for patients, parents, and caregivers. Plain-language explanations of symptoms, diagnosis, and treatment, plus photos, illustrations, animations, "how-to" videos, quizzes, and self-assessment tools. - Professional Version (
/professional): for clinicians and medical students. Retains pathophysiology, drug dosing, and clinical detail, with clinical calculators and reference guides. On the Chinese site, a dialog asks visitors to confirm they are medical professionals before entering. - A separate Merck Veterinary Manual exists; the Chinese site notes it is available in English only.
Both editions come from the same editorial pipeline and differ only in how the content is rewritten. The editorial staff page explains that internal editors adapt the material for non-specialist health care professionals (Professional Version) and for consumers (Consumer Version).
Content and Features
The manuals cover thousands of topics across all fields of medicine, browsable by organ system and condition or searchable by keyword. Every topic page names its author and peer reviewer together with full-review and last-update dates — the consumer topic below, for example, credits the physician who wrote the chapter and the specialists who reviewed it, a clear contrast with anonymously written wiki-style references.
Beyond articles, the site hosts a large multimedia library: extensive photos and illustrations, hundreds of animations, procedural videos, 3D models, and health quizzes. Free iOS and Android apps (Professional, Consumer, and Veterinary editions) require no registration or subscription, though some features such as the drug reference and interactive case simulations are English-only. The site also offers an AI-enhanced search; the disclaimer explicitly warns that AI-generated answers may contain errors and should be checked against other reliable sources.
How the Content Is Produced
The editorial process mirrors that of major medical textbooks: chapters are written by more than 300 external expert authors, reviewed by an independent board of over two dozen peer reviewers, checked for drug dosing by an external pharmacologist, and finalized by in-house physician editors and the editor-in-chief (see the editorial process).
The publisher stresses its editorial independence: authors and reviewers cannot be Merck & Co. employees or speak for its products, and no other part of the company — R&D, marketing, public relations, legal — may influence the content. The site carries no registration fees, ads, or product promotion of any kind.
Terms of Use and Copyright
- Medical disclaimer: the disclaimer states that all content is for informational purposes only and is not a substitute for medical advice, diagnosis, or treatment. Content reflects medical practice in the United States and may differ from local guidelines elsewhere; the original text is English, and translations may introduce errors.
- Copyright, no commercial reuse: content is copyrighted. The publisher's terms of use prohibit using the content — text, images, audio, or video — for public or commercial purposes without written permission, and prohibit scraping or data mining. Reuse requests go through the site's permissions page. In short: free to read, not open content.
- Privacy: the site requires no account, and the publisher says it does not collect personal data; privacy is handled under MSD's corporate privacy program (msdprivacy.com).
When It's Useful
- Reading a plain-language explanation of a condition, symptom, test, or treatment before or after a doctor's visit;
- Looking up the meaning of a medical term, a common lab test, or a vital-sign range your clinician mentioned;
- For medical students and health professionals, quick reference via the Professional Version and its clinical calculators;
- As a controlled starting point for reliable health information instead of search-engine content aggregation.
Limitations
- It is a reference, not a care provider: nothing on the site is medical advice, and any real condition still requires an in-person clinician.
- Content is aligned with US medical practice; recommendations, drug names, and availability may differ from guidelines in other countries. The publisher advises consulting local providers as well.
- The English text is the original; translations can lag or introduce errors, and several features (drug reference, interactive cases, the veterinary manual) are English-only.
- No alternative-medicine or folk-remedy content, no personalized health records or consultations, and — with no account system — no bookmarks or reading history.
- Reuse is restricted: commercial use and scraping are prohibited by default, unlike CC-licensed open-content sites.
Comparable Sites
- MedlinePlus: the US National Library of Medicine's free consumer health information service, in English and Spanish, similar in purpose to the Consumer Version.
- Mayo Clinic Diseases & Conditions: patient-education articles published by Mayo Clinic, primarily in English.
