Most research articles you find through NIH databases like PubMed and PubMed Central are peer reviewed, but not all of them. The answer depends on what type of “NIH article” you’re looking at, because the NIH produces, funds, and archives several different kinds of content, each with its own review process.
Research Articles in PubMed and PubMed Central
The vast majority of research papers you’ll find through PubMed are published in peer-reviewed journals. PubMed is a search engine maintained by the National Library of Medicine, and its core collection, known as MEDLINE, consists of citations from journals that meet specific quality standards. When a journal article carries a MEDLINE index, it has gone through the traditional peer review process at whatever journal published it. Peer review means independent scientists evaluated the study’s methods, data, and conclusions before the journal agreed to publish it.
PubMed Central (PMC) is a related but different resource. It’s a full-text archive that stores complete articles rather than just citations. PMC includes articles from journals selected by the National Library of Medicine for archiving, plus individual articles deposited to comply with funder requirements. The NIH Public Access Policy, updated in 2024, requires researchers who receive NIH funding to submit their accepted manuscripts to PubMed Central upon acceptance for publication. Starting July 1, 2025, these must be made publicly available with no embargo. These deposited manuscripts have been peer reviewed by the journals that accepted them.
However, PMC also contains preprints, which have not been peer reviewed. This is an important distinction.
How to Spot Preprints in NIH Databases
Through its Preprint Pilot (Phase 2 launched in January 2023), the NIH archives preprints from servers like bioRxiv, medRxiv, arXiv, and Research Square. These are early-stage manuscripts that acknowledge NIH support or have an NIH-affiliated author but have not gone through journal peer review.
The NIH takes clear steps to label these. Every preprint record in PMC and PubMed includes a prominent information panel stating that the article has not yet been peer reviewed, along with a link explaining the Preprint Pilot. A “Preprint” indicator also appears in the citation metadata, the citation tool, and in search results. If you want to exclude preprints from your PubMed searches entirely, you can add NOT preprint[pt] to your query. The preprint servers themselves are required to clearly mark content as not certified by peer review before the NIH will archive from them.
NIH-Funded Research vs. NIH-Authored Content
There’s a meaningful difference between research the NIH funds and content the NIH writes itself. The NIH is the largest public funder of biomedical research in the world, and the papers produced by its grantees are published in independent, peer-reviewed journals. The NIH doesn’t control the peer review of those papers. That’s handled by whichever journal the researchers submit to.
Content authored directly by NIH staff goes through a different process. Any work-related manuscript written by an NIH employee must pass through an internal clearance process before it can even be submitted to a journal. This involves supervisory review for accuracy and appropriateness, approval by the employee’s institute or center director (or a designee such as a scientific director or lab chief), and in cases of joint authorship, separate approval from each author’s respective institute. Intramural scientists, those who work in NIH’s own laboratories, have their manuscripts reviewed by lab and branch chiefs and scientific directors before submission. After clearing this internal process, the paper still goes through standard journal peer review like any other submission.
Consumer Health Pages on NIH Websites
If you landed on a health topic page from MedlinePlus or a fact sheet from a specific NIH institute, that’s a different category entirely. These aren’t peer-reviewed research articles. They’re consumer health resources written and maintained by NIH staff or contractors, and they follow their own editorial standards.
MedlinePlus health topics are updated as new information becomes available, with broken links checked daily. Medical test pages are fully reviewed at least every three years. Genetics content is reviewed by genetics experts before posting and with each major revision, with additional input from patient advocacy groups. The medical encyclopedia articles on the site include the names of medical reviewers and a review date at the bottom of each page. Drug and supplement pages are revised when important changes occur and show a “last revised” date.
These pages are editorially reviewed and fact-checked, but they are not “peer reviewed” in the scientific journal sense. They’re summaries of existing research, designed to be readable and useful for the general public. You can generally trust them as reliable health information, but they serve a completely different purpose than a peer-reviewed study.
How NIH Grant Applications Are Reviewed
One more layer worth understanding: the NIH also peer-reviews the research proposals it funds, though this is separate from the peer review of published articles. NIH uses a two-stage system. In the first stage, panels of volunteer scientists (called study sections) evaluate grant applications on five criteria: significance, quality of the investigators, innovation, scientific approach, and research environment. In the second stage, advisory councils at each NIH institute review the applications for relevance to the institute’s mission. Final funding decisions rest with institute directors.
This means NIH-funded research has typically passed two rounds of expert scrutiny before a single experiment is run: one to win the grant, and another when the resulting paper goes through journal peer review. That double layer of evaluation is one reason NIH-funded research is widely considered high quality, though it doesn’t guarantee any individual paper is free of errors or limitations.
Quick Way to Check Any Article
When you pull up an article in PubMed or PMC, look at the citation metadata near the top. If it shows a journal name and a standard volume/issue citation, it’s almost certainly peer reviewed. If you see a “Preprint” label or a banner warning that the work hasn’t been certified by peer review, treat it as preliminary. For consumer health pages on sites like MedlinePlus or individual NIH institute websites, look for the “last updated” or “last reviewed” date and reviewer names at the bottom of the page. These tell you the content has been editorially vetted, even if it hasn’t gone through formal peer review.