NLM citation style is a reference format developed by the National Library of Medicine for biomedical and life sciences writing. It groups in-text markers with a numbered or author-based reference list, and it is the format PubMed itself uses to display journal citations. If your professor or journal asks for “NLM style,” “Vancouver-based style,” or “Citing Medicine format,” this guide covers the in-text rules, the reference list formats for the most common source types, and the mistakes that cost students the most points. It sits alongside our other citation style guides if you need to compare NLM against a different format your class allows.
What Is NLM Citation Style?
NLM citation style comes from Citing Medicine, the official NLM Style Guide for Authors, Editors, and Publishers, produced by the National Library of Medicine. It is the citation system behind PubMed’s own reference display, and it is closely related to Vancouver style, which many journals use as their house format. Because the two share the same numbered in-text approach and similar reference punctuation, style guides often use “NLM” and “Vancouver” interchangeably, though NLM is the fuller, more detailed manual of the two.
NLM style is the standard citation format in fields that publish through PubMed and similar biomedical databases, including:
- Medicine
- Nursing
- Neuroscience
- Public health
- Pharmacy
- Biomedical research
The core goal of NLM style is the same as any citation system: let a reader trace your source back to where you found it. What sets NLM apart is its emphasis on precise author initials, abbreviated journal titles, and a numbered reference list that mirrors how PubMed catalogs articles. For the full technical rules beyond what a class paper needs, the Citing Medicine manual on the NCBI Bookshelf is the definitive source.
The Three NLM In-Text Citation Systems
NLM style gives writers three options for in-text citations. Your instructor or target journal usually specifies which one to use, so check the assignment guidelines or author instructions before you start. Whichever system you pick, stay consistent throughout the paper.
| System | How It Works |
|---|---|
| Citation-Sequence | References are numbered in the order they first appear in the text. A superscript number goes at the end of the sentence, before the period. The reference list follows the same numeric order. |
| Citation-Name | References are numbered by alphabetical order of the author’s surname in the reference list first, then that same number is used every time the source appears in the text. |
| Name-Year | The in-text citation uses the author’s surname and the publication year in parentheses, similar to APA. The reference list is arranged alphabetically instead of numerically. |
A citation-sequence in-text marker looks like this in practice: “Playing memory-training games improved recall scores in older adults.1” A name-year citation for the same claim would read “Playing memory-training games improved recall scores in older adults (Alvarez 2023).” The reference list format itself does not change between these three systems. Only the numbering or author-year marker and the sort order of the list change.
NLM Reference List Format by Source Type
Every NLM reference follows the same underlying logic: author initials with no periods between them, a plain article or book title, an abbreviated journal name, and a publication date placed before the volume and issue. The examples below use the citation-sequence numbering. Drop the number if your paper uses name-year style instead.
Journal Article
Format: Author AA, Author BB. Article title. Journal Title Abbreviated. Year;Volume(Issue):Pages.
1. Alvarez ML, Chen JW. Working memory training in adults over 65. J Cogn Aging. 2023;12(4):301-9.
Journal titles are abbreviated using the format found in the NLM Catalog of Journals, and up to the first three authors are listed before adding “et al.” for anything beyond that.
Journal Article, Online-Only
Format: Author AA. Article title. Journal Title [Internet]. Year [cited Year Month Day];Volume(Issue):Pages. Available from: URL
2. Osei K. Telehealth adherence in rural clinics. Rural Health J [Internet]. 2024 [cited 2026 Sep 14];9(2):55-63. Available from: https://ruralhealthjournal.org/articles/2024-adherence
Book
Format: Author AA. Book title. Edition. Place of Publication: Publisher; Year.
3. Patel R. Foundations of clinical pharmacology. 4th ed. Boston: Meridian Press; 2022.
For book-length sources, including edited collections, the how to cite a book guide walks through the author and editor placement rules in more depth.
Website
Format: Author/Organization. Page title [Internet]. Place of Publication: Publisher; Date of Publication [cited Year Month Day]. Available from: URL
4. National Institute of Mental Health. Anxiety disorders [Internet]. Bethesda (MD): National Institutes of Health; 2024 [cited 2026 Sep 14]. Available from: https://www.nimh.nih.gov/health/topics/anxiety-disorders
Website citations need a “date cited” because online content changes. See the site’s guide to citing a website for how to handle missing publication dates. The full sample set of official formats, including book chapters and conference papers, is available on the NLM Uniform Requirements page.
DOIs, PMIDs, and PMCIDs
Many NLM references now include a persistent identifier after the page numbers. A DOI (Digital Object Identifier) points to the article through Crossref regardless of where it moves online. A PMID (PubMed Identifier) is the unique number PubMed assigns to an indexed article, and a PMCID is the parallel identifier used by PubMed Central for the free full-text version. None of the three is mandatory in the core NLM format, but journals in medicine and public health increasingly expect at least a DOI when one exists.
5. Garcia FM, Nkemelu D. Sepsis biomarkers in pediatric ICUs. Crit Care Med. 2025;53(3):412-20. doi: 10.1097/CCM.0000000000005812. PMID: 39812345.
Common NLM Citation Mistakes
NLM’s formatting rules are precise, and small punctuation slips are the most common way students lose points. The table below covers the errors that show up most often.
| Mistake | Why It Matters |
|---|---|
| Periods between author initials | NLM style drops periods between initials. Write “Alvarez ML” instead of “Alvarez, M.L.” |
| Full journal titles | Journal names must be abbreviated per PubMed’s standard list, not spelled out in full. |
| Mixing in-text systems | A paper cannot switch between citation-sequence, citation-name, and name-year partway through. Pick one and stay consistent. |
| Missing “cited” date on web sources | Online sources change or disappear. Leaving out the date you accessed the page breaks the NLM format. |
| Listing every author past three | Once a source has more than three authors, list the first three and add “et al.” |
NLM vs. Vancouver Style
NLM and Vancouver style share the same numbered, superscript approach to in-text citations, and their reference list punctuation is nearly identical. The difference is scope: Vancouver style is a short set of author guidelines maintained by the International Committee of Medical Journal Editors, while NLM’s Citing Medicine is a full-length manual that covers far more source types in greater detail, from government reports to database entries. In practice, most citation software that offers “Vancouver” as an option will produce a reference list close enough to NLM format for coursework. If a journal specifically requests NLM style, however, use the official NLM reference format used by PubMed rather than a generic Vancouver template, since PubMed’s abbreviation and punctuation rules are stricter. A Vancouver-style citation generator is a reasonable starting point either way, as long as you double-check the output against the format tables above.
Frequently Asked Questions
Is NLM citation style the same as Vancouver style?
They are closely related but not identical. Both use numbered, superscript in-text citations and similar reference punctuation, but NLM’s Citing Medicine manual covers far more source types in more detail than the shorter Vancouver guidelines.
Which NLM in-text citation system should I use?
Check your assignment sheet or the target journal’s author instructions first. If neither specifies, citation-sequence is the most common default because it lets readers see the order sources were used as they read.
How many authors do I list in an NLM reference before using “et al.”?
List the first three authors, then add “et al.” for any authors beyond that. This applies to journal articles, books, and most other source types in NLM style.
Do NLM citations need a DOI?
A DOI is not required in the core NLM format, but many journals now include it after the page numbers when one is available, since it gives readers a permanent link to the source.
Where can I find the official NLM style rules?
The complete rules live in Citing Medicine, published on the NCBI Bookshelf. It is the authoritative source for any source type not covered in this guide.
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Terry is a Chicago-based writer and editor who creates practical, student-friendly guides on essay writing, research, and citation styles (APA, MLA, and Chicago). He’s spent 15+ years editing educational content and building clear examples that help readers apply rules without guessing. When he’s not revising drafts, he’s usually turning messy notes into clean outlines and hunting down the one detail everyone skips.