AMA vs Vancouver vs ICMJE vs NLM: A Medical Writer's Guide to Citation Styles

Open a journal's instructions for authors, or a company style guide, and you keep meeting the same four names: AMA, Vancouver, ICMJE, and NLM. It is easy to assume they are four competing citation styles you have to learn separately. They are not. The short version: all four are numbered citation systems, and three of them, Vancouver, ICMJE, and NLM, are essentially one family under different names. The only real choice you face is AMA versus that family.

Here is how they actually relate, the one difference that trips people up, and how to know which one applies to you.

They are all numbered systems

Unlike the author-date styles used in psychology and the social sciences, such as APA and Harvard, where the text carries "(Smith, 2021)", every style here is a numbered system. You cite a source with a number, and the reference list is ordered by the sequence in which sources first appear in the text. That shared design has a practical upside: moving between these styles is reformatting, not rewriting. The structure of your references does not change, only the small typographic rules do.

Vancouver, ICMJE, and NLM are one family

This is the part that clears up most of the confusion.

• Vancouver is the name of the style. It comes from a 1978 meeting of medical journal editors in Vancouver, who set out to standardize manuscript and reference formatting.
• That group became the International Committee of Medical Journal Editors (ICMJE), which maintains the "Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals." The reference style described in those Recommendations is Vancouver, and well over a thousand journals follow it.
• ICMJE does not spell out every formatting detail itself. It points authors to the US National Library of Medicine (NLM) and its guide "Citing Medicine" for the specifics. This is the same style PubMed and MEDLINE use to display references.

So when one journal says it "uses Vancouver," another says it "follows ICMJE," and a third asks for "NLM style," they are describing the same family, with only minor house variations. If you can format a reference for PubMed, you can format it for any of the three.

Where AMA is genuinely different

AMA is the odd one out, and it is the one many writers in US medical communications actually use day to day.

AMA refers to the American Medical Association Manual of Style, now in its 11th edition (2020). It is the house style of JAMA and the JAMA Network journals, and it is widely adopted across US medical publishing and pharmaceutical promotional materials. It is also a numbered system, but it has its own rulebook, and a few differences matter in practice:

• In-text citations. AMA uses superscript Arabic numerals. Vancouver and ICMJE journals vary: some use superscript, others use numbers in parentheses (1) or square brackets [1], depending on the journal's own instructions.
• The author cutoff. This is the classic difference. In AMA, if a reference has more than six authors, you list the first three followed by "et al." In Vancouver and ICMJE, if there are more than six authors, you list the first six followed by "et al."
• Smaller specifics. The two families share NLM-style abbreviated journal titles, but differ in details such as punctuation, how page ranges are condensed, and how DOIs and online-access dates are presented.

At a glance

So which one should you use?

Most of the time, you do not choose. The style is dictated for you by one of two things:

• If you are writing for a journal, its instructions for authors tell you exactly which style and which variations to use. Follow them literally, because editors do reject on formatting.
• If you are writing promotional or medical materials, your company or agency style guide sets the standard, usually in an SOP. In US pharmaceutical promotion, that standard is frequently AMA.

The practical discipline is simple: confirm the required style before you start, apply it consistently, and do not mix conventions within a document. Switching styles late is tedious and error-prone, which is exactly why it is worth settling first.

Style is the last 5%. The source is the work.

It is easy to spend an afternoon perfecting superscripts and "et al" rules and lose sight of the point. Citation style is formatting. It is the final, visible layer on top of the part that actually determines whether a claim survives review.

Whatever style your SOP mandates, every reference still has to do three things: it has to exist, it has to actually support the specific claim in its population and context, and it has to match the right label. A flawlessly AMA-formatted citation attached to a paper that does not support the sentence is still a finding waiting to happen in MLR review. Reviewers check the substance, not the superscripts. That is also why anchoring each citation to the exact supporting line does more for your review timeline than any formatting rule.

Automate the easy part

Getting the style right should be mechanical, so automate it. Our free AMA citation generator turns a PubMed record into a clean, correctly formatted short AMA citation in one paste, so you spend your time on substantiation rather than punctuation.

And when the question moves from "is this formatted correctly?" to "does this source actually support the claim?", that is what PharmaText.ai is built for. It checks every claim against your uploaded sources, in whatever citation style your team uses, and flags anything unsupported, mis-sourced, or contradicting the label before it reaches review.

Related: see what actually needs a reference, why AI-generated citations are often fake, and linking and anchoring.

Sources: author and formatting rules from the AMA Manual of Style, 11th edition; the ICMJE Recommendations; and the US National Library of Medicine, Citing Medicine and its sample references.