A Guide to NLM Citation: Correctly Citing Medical Research Sources

By Christopher Smith Jun 29, 2025

You’re working on a research paper about a medical topic. You’ve spent hours searching databases like PubMed and have found some amazing journal articles. You’ve written up your findings, but now you’ve reached the final, confusing step: citing your sources in "NLM style."

What does that even mean? It can feel like a complicated code, but don't worry. This guide is here to make it simple.

Think of citations in medicine like a patient's medical record. Every piece of information must be clear, accurate, and easy to trace back to the source. NLM citation is the system that makes this possible. It ensures that doctors, scientists, and students are all speaking the same language when they talk about research. Learning it is a key part of learning how to avoid plagiarism while incorporating research in your writing.

This guide will walk you through everything you need to know about NLM style, with simple explanations and clear examples.

What Is NLM Style and Why Is It Used in Medicine?

NLM stands for the National Library of Medicine, which is the largest medical library in the world. The NLM created this specific citation style to be used in medicine, nursing, and other health science fields. If you’ve ever used PubMed, the giant database for medical research, then you have seen NLM style in action.

Why is this so important in medicine?

Accuracy is Critical: In health care, mistakes can be serious. A clear and consistent citation style ensures that a doctor or researcher can quickly find the original study to verify its findings.
It Builds Trust: When you cite your sources correctly, you are showing your reader that you have done your research carefully and that your information is based on real science.
It Prevents Plagiarism: It is the honest way to give credit to the scientists who did the original work.

Even small mistakes in your citations can make your work look less professional, which is why citation errors lower your grade and how to avoid them.

The Two Simple Parts of NLM Citation

Like most citation styles, NLM has two parts that work together as a team:

In-Text Citations: These are small numbers that you place inside the sentences of your paper, right after you state a fact or idea from another source.
The Reference List: This is the numbered list at the end of your paper that gives the full details for every source you cited.

The in-text number is like a signpost that points the reader to the full source information in your reference list.

Part 1: How to Use In-Text Citations in NLM

NLM uses a simple number system called "citation-sequence." It sounds fancy, but it's very easy to understand.

The very first source you mention in your paper is given the number "1".
The second source you mention is number "2".
The third is number "3," and so on.

If you mention source #1 again later in your paper, you just reuse the number "1". You don't create a new number for it.

You can format these numbers in two ways. Ask your professor which one they prefer.

Using Parentheses: This is the most common way.
- Example: A recent study showed that vitamin D is essential for bone health (1).
Using Superscript Numbers: These are small numbers that sit just above the line.
- Example: A recent study showed that vitamin D is essential for bone health¹.

Part 2: How to Build Your NLM Reference List (With Examples!)

Your reference list at the end of your paper will be a numbered list (1, 2, 3...). The numbers in this list will match the numbers you used for your in-text citations. Here are the templates for the most common types of sources you’ll use in medical research.

Example 1: Citing a Journal Article (The Most Important One!)

This is the format for a research article you found in a scientific journal.

Template: Author(s). Article title. Abbreviated Journal Title. Year Month Day;Volume(Issue):Pages.
Real Example: Kaur J, Kumar V, Sharma R. Effects of exercise on mental health. J Clin Psychol. 2024 Jan;80(1):115-30.
Key Tips:
- Authors: Write the last name and then the first and middle initials (with no periods). For example, John David Smith becomes Smith JD.
- Journal Title: NLM uses specific abbreviations for journal titles (e.g., New England Journal of Medicine becomes N Engl J Med). You can find the correct abbreviation by searching the NLM Catalog online.
- Punctuation: Notice there is no comma after the journal title or a colon after the volume number. The details matter!

Example 2: Citing a Book

Template: Author(s). Book title. Edition number (if not the first). Place of publication: Publisher; Year.
Real Example: Carlson B. Human embryology and developmental biology. 5th ed. Philadelphia (PA): Saunders; 2014.
Key Tips:
- The place of publication is followed by a colon, then the publisher's name.
- If the book has editors instead of authors, write their names followed by ", editors.".

Example 3: Citing a Website or Webpage

Template: Author or Organization. Title of the page [Internet]. Place of publication: Publisher; Date of publication [cited Year Mon Day]. Available from: URL
Real Example: Centers for Disease Control and Prevention. About CDC [Internet]. Atlanta (GA): CDC; 2023 May 15 [cited 2025 Jun 29]. Available from: https://www.cdc.gov/about/index.html
Key Tips:
- Always include "[Internet]" in brackets after the title.
- The "cited" date is the date you looked at the website. This is important because webpages can change.

Example 4: Citing a Chapter in an Edited Book

Template: Author(s) of chapter. Title of the chapter. In: Editor(s), editors. Title of the book. Edition. Place of publication: Publisher; Year. p. page numbers of chapter.
Real Example: Relling MV, Evans WE. Pharmacogenomics. In: Brunton LL, Chabner BA, Knollmann BC, editors. Goodman & Gilman's the pharmacological basis of therapeutics. 13th ed. New York: McGraw-Hill; 2018. p. 115-34.

Final Tips for NLM Success

Be a Detective with Details: NLM style is very specific. Pay close attention to every period, comma, and semicolon in the templates.
Use the Right Tools: Use the online NLM Catalog to find the official abbreviations for journal titles. Don’t guess!
Check Your Work: Online citation generators can be a good start, but they often make small mistakes with NLM style. Always proofread the citations they create and fix any errors. This is a key part of how to identify and fix weak arguments in your academic writing—strong citations create a strong foundation.

You Can Cite Like a Pro!

NLM citation can seem intimidating at first, but it is a very logical and consistent system. Once you get the hang of the format for a journal article, you will be well on your way to mastering it.

By taking the time to cite your sources correctly, you are showing your respect for the scientific process and proving that you are a careful, credible researcher. It's a fundamental skill for anyone entering the medical field. Use this guide, pay attention to the details, and you’ll be citing your sources perfectly in no time.