Evidence Based Medicine

This guide is designed to assist health care professionals and students become effective and efficient users of the medical literature.

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What is PubMed?

PubMed is the National Library of Medicine's (NLM) platform for searching MEDLINE.

Besides MEDLINE, PubMed also includes PubMed Central and Bookshelf.

For more information about PubMed, see:

To search PubMed, use these links:


MEDLINE is produced by the NLM, is the premiere database of biomedical citations, and is freely available.

  • Coverage: generally 1946 to the present
  • Indexes 5,400+ international biomedical journals
  • Includes primarily journal articles, reviews, letters, editorials, comments
  • Does include some books from NCBI's Bookshelf
  • Abstracts are available for most entries
  • MEDLINE is available for searching through NLM's PubMed, commercial vendors, and universities.

What is MeSH?

MeSH banner image with the text "MeSH (Medical Subject Headings) is the NLM controlled vocabulary thesaurus used for indexing articles for PubMed."

"MeSH (Medical Subject Headings) is the NLM controlled vocabulary thesaurus used for indexing articles for PubMed." -- NCBI. NLM. MeSH

MeSH consists of sets of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.  An advantage of controlled vocabularies, like MeSH, is that a single term has been used to represent a particular concept no matter how it was referred to in the original article.

What you need to know:

  • PubMed/MEDLINE uses MeSH for indexing database articles.
  • 6-15 subject headings are assigned per article, with up to 3 assigned for major emphasis of the article.
  • MeSH is updated annually to reflect current terminology usage.
  • MeSH allows for more precise subject searching. Articles are indexed to the most specific term available.
  • Using MeSH to search MEDLINE allows the searcher to apply subheadings or add major emphasis.

Building and Refining Your PubMed Searches

Database searching is a process in which you put pieces together to build your search, try your search, and revise your search until you are satisfied with the results.

Use these steps to help guide you through that process.  You may need all or only some of these steps.

Step 1 - Define your Question.

Step 2 - Select text words and MeSH terms that best represent your concepts.

  • Combining both text words and MeSH terms retreives the best results.

Step 3 - Combine Concepts with AND, OR, NOT.

  • AND is used to connect concepts when both or all must be present = Nutrition AND Infant
  • OR is used to group synonyms when at least one must be present = Nutrition OR Diet
  • NOT is used to eliminate articles containing the term.  NOT can be tricky so use it cautiously. = Diet NOT Vegetarian

Step 4 - Refine Your Search with Filters.

  • The filters for age, article type, and publication date can be especially useful.

Step 5 - Try Running Your Search.

  • If you are happy with the result, you are done.  If you are not sure, review your search for possible revisions or continue with Step 6.

Step 6 - Select Terms for Type of Question and Type of Study.

Step 7 - Consider Adding a Term Related to Time.

Step 8 - Try Running Your Search Again.

  • If you are still not satisfied, review your search again for possible revisions or move on to Steps 9 through 11.

Step 9 - Find a Particularly Relevant Article in Your Results.

  • Look at the MeSH terms for the article and use them to search.

Step 10 - Look at the Similar Articles Suggested by PubMed.

Step 11 - Try Your Search in Other Databases.

Step 12 - Consult a Librarian.

  • When you have tried these steps and still not found what you wanted, ask for help.


Getting Too Much With Your PubMed Search?

Try these techniques for limiting your results:

  • Use AND with another concept
  • Limit to English
  • Limit by Age, Sex, Human
  • Limit to Publication Type (for example: Randomized Controlled Trial or Review)
  • Use Subheadings (for example: Diagnosis or Therapy)
  • Use a more specific term (Femoral Neck Fractures instead of Hip Fractures)
  • Restrict to Major MeSH Topic
  • Choose "Do not include MeSH terms found below this term in the MeSH hierarchy"
  • Use Text Word in Title

Not Getting Enough With Your PubMed Search?

Try these techniques for increasing your results:

  • Use OR with synonymous/related concepts
  • Include all languages (English abstracts are often available)
  • Remove all Limits
  • Do not restrict to Publication Types
  • Choose All Subheadings
  • Use a broader term (Eye Diseases instead of Retinal Diseases)
  • Do not Restrict to Major MeSH Topic
  • Do not choose "Do not include MeSH terms found below this term in the MeSH hierarchy"
  • Truncate text words (recommend*)
  • Look at the "Similar Articles" list generated by PubMed


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