The National Library of Medicine is a credible source of health information, but whether a specific page carries the NLM’s backing depends on where you found it. Content the NLM writes itself, like MedlinePlus, is directly reviewed and maintained by library staff. Content the NLM indexes, like the citations you find through PubMed, is a different matter: the library catalogs those articles but does not endorse their conclusions. Understanding that split is the single most useful thing to know before relying on anything with an “nlm.nih.gov” address.
What the NLM Stands Behind and What It Only Indexes
The NLM runs two kinds of resources, and they carry very different weight.
MedlinePlus is the consumer health portal. NLM staff write, curate, and review the material, translating established medical knowledge into plain language. Health topics are updated as new information becomes available, and links are checked and fixed daily.1National Library of Medicine. Review and Update of Content on MedlinePlus The site is available in 53 languages.2National Library of Medicine. Health Information in Multiple Languages When you read something on MedlinePlus, the NLM is standing behind it.
PubMed is different. It is a search engine for biomedical literature. MEDLINE is the selectively indexed subset within PubMed. PubMed Central (PMC) is a free full-text archive that includes articles deposited because they were funded by NIH grants, whether or not the journal itself passed MEDLINE review.
The NLM is explicit about what indexing means: “the presence of any article, book, or document in these databases does not imply an endorsement of, or concurrence with, the contents by NLM, the National Institutes of Health (NIH), or the U.S. Federal Government.”3National Library of Medicine. Disclaimer Finding a study on PubMed means a journal published it and the NLM cataloged it. It does not mean the library reviewed the conclusions and agrees.
You can check whether a specific journal passed MEDLINE review by looking up its record in the NLM Catalog. A “Current Indexing Status” for MEDLINE tells you the journal cleared the selection process.4National Library of Medicine. Frequently Asked Questions Articles from non-MEDLINE journals that still appear in PubMed have not.
How MEDLINE Vets the Journals It Indexes
The quality gate that does exist sits at the journal level, not the article level. The NLM describes its review as rigorous and multi-step, and it evaluates five elements before accepting a journal into MEDLINE:5National Library of Medicine. Journal Selection for MEDLINE
- Scope and coverage in biomedicine or the life sciences.
- Editorial policies, including an explicit peer-review process and clear ethical policies.
- Scientific or methodological rigor, meaning valid, important, and original research.
- Professional production and consistent publication.
- Meaningful impact on the scientific literature in the field.
One institutional shift is worth flagging. Until 2025, journal review was handled by the Literature Selection Technical Review Committee, a federal advisory committee established in 1987 that provided independent recommendations.6National Library of Medicine. About the Literature Selection Technical Review Committee (LSTRC) The committee was terminated in 2025, and the NLM announced a modernized selection process. The five-element framework remains in place, but the independent advisory body that formerly guided journal selection no longer exists.
Standards for External Links on MedlinePlus
MedlinePlus does not link outward to just any health site. The NLM publishes the criteria external organizations must meet:7National Library of Medicine. Guidelines for Links
- The organization’s mission must align with providing accurate, science-based health information.
- The site cannot exist to sell or promote a product, service, or belief.
- Content must be original to the site, not reproduced from elsewhere.
- Ad-free pages are preferred; where ads exist, they must be clearly separated from health content, and advertisers cannot influence the selection or editing of that content.
- Health information must be free to view, with no required registration or payment.
- The organization must publish its advisory board members or consultants with health expertise.
Because these standards are public, anyone can check whether the NLM is holding to them.
What Happens When a Study Turns Out to Be Wrong
No indexing system prevents flawed papers from being published. What matters is how errors are handled once they surface. When a journal publishes a retraction, the NLM creates links in PubMed between the retraction notice and the original article. The original citation gets a “Retracted Publication” tag; the retraction notice gets a “Retraction Notice” tag.8National Library of Medicine. Errata, Retractions, and Other Linked Citations in PubMed Retracted papers stay in the database rather than disappearing, preserving the scientific record while warning readers.
One caveat worth knowing: the NLM does not distinguish between retractions for honest error and retractions for misconduct. Both carry the same tag. A retraction label doesn’t automatically mean fraud, but it does mean the paper’s conclusions should not be relied on.
Why Funding Structure Matters
The NLM operates on federal appropriations. Its FY 2024 enacted budget was approximately $495 million, allocated across competitive grants, contracts, and direct programs.9National Library of Medicine. FY 2024 Congressional Justification – National Library of Medicine The library does not carry advertising on its core platforms and does not charge users for PubMed, MedlinePlus, or ClinicalTrials.gov.
This removes the most common source of bias in health information. A commercially funded health website has incentives to frame conditions and treatments in ways that drive ad revenue or please sponsors. The NLM does not. It sits within the NIH, which sits within the U.S. Department of Health and Human Services, and its budget is a public document reviewed by Congress.10National Library of Medicine. NLM by Organization
Privacy When You Search Sensitive Topics
People often use the NLM to look up mental health conditions, sexually transmitted infections, substance use, and other topics they would not want linked to their name. The library’s privacy policy addresses this directly: the NLM does not collect personally identifiable information unless you voluntarily provide it, and it does not associate search terms or browsing patterns with individual users.11National Library of Medicine. NLM Web Policies Web logs are periodically deleted, and any aggregated data shared with contracted researchers cannot be linked back to individual visitors. The NLM does not sell or share personal information unless required by law.
When electronic medical records or patient portals link users to MedlinePlus, diagnosis codes may be transmitted so relevant information appears, but no personally identifiable information is collected in that process.11National Library of Medicine. NLM Web Policies
Institutional Changes to Watch
Two shifts affect how NLM credibility should be assessed going forward. The first is the 2025 termination of the LSTRC noted above. The second is a proposal in the FY 2026 federal budget to consolidate the NLM into the National Institute of General Medical Sciences, folding it together with several other institutes into a larger combined entity.12National Institutes of Health. Overview of FY 2026 Executive Summary The stated rationale is minimizing redundancies and improving collaboration. Whether the restructuring affects the quality or independence of NLM resources is not yet known.
The databases, editorial standards, and privacy protections described above remain in place. If you use NLM resources regularly, it is worth watching for changes to the journal selection process and to MedlinePlus editorial oversight as the proposed reorganization moves forward.