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Expert Searching

1. When to Use PubMed

PubMed is a platform that indexes journal articles and more back to 1947. It covers the areas of medicine, nursing, dentistry, veterinary medicine, health care systems, preclinical sciences, and related areas. PubMed is developed and maintained by the National Library of Medicine (NLM) and the National Center for Biotechnology Information (NCBI), both at the National Institutes of Health (NIH) in Bethesda, MD. As of December 2020, PubMed contains over 30 million records. PubMed is a platform that contains MEDLINE, PubMed Central, and additional PubMed records.

2. PubMed Cool Tools

Clinical Queries

Use Clinical Queries to enable pre-made filters applying to different clinical research areas. Results are delineated into clinical studies, systematic reviews, and medical genetics. Enter your search exactly as you would in the PubMed search box.

For more information, see:

Journals in NCBI Databases

Use Journals in NCBI Databases to limit your search to a specific journal or to find out more information about journals indexed in MEDLINE. text

Single Citation Matcher

Use the Single Citation Matcher to find citations in PubMed. You may enter or omit any field.

Special Queries

Searchers at the National Library of Medicine have created search filters for multiple common topics. See and enable them on the PubMed Special Queries page.

3. How to Use MeSH: Medical Subject Headings

Controlled Vocabulary: MeSH

  • MeSH stands for Medical Subject Headings. It is a controlled vocabulary of terms assigned to records to make them discoverable.
  • These are a standardized set of terms that are used to bring consistency to the searching process. In total, there are approximately 29,000 MeSH terms, and they are updated annually to reflect changes in terminology.
  • Use the MeSH database to identify Medical Subject Headings (MeSH) which will help you to find literature indexed with the MeSH term.
  • Using MeSH terms helps account for variations in language, acronyms, and British vs. American English.
  • MeSH can be searched from the MeSH Database
  • Terms are arranged hierarchically by subject categories with more specific terms arranged beneath broader terms. MeSH terms in PubMed automatically include the more specific MeSH terms in a search. This is called "explode."
  • To turn off this automatic explode feature, click on the button next to, "Do not include MeSH terms found below this term in the MeSH hierarchy" in the MeSH record or type [mesh:noexp] next to the search term, e.g.neoplasms [mesh:noexp]. See next page for additional information on no explode.
  • Use the PubMed Search Builder on the right side of the screen to add your selected MeSH term to the box, and click Search.

Explode, No Explode, and Major Heading

  • Explode will search with all narrower headings beneath the main heading you have chosen. PubMed will default to explode any MeSH term you search.
  • No Explode will only search for your chosen MeSH term without including any of the narrower headings in the MeSH hierarchy. You can select this option from the MeSH record.
  • Major Heading will narrow your search to only find MeSH terms listed as a major topic of an article. You can select this option from the MeSH record. Major headings are shown in the article record with an asterisk.


MeSH terms can be made more specific by the addition of correlated or free-floating subheadings.

  • When in the MeSH record, add subheadings by clicking on the boxes next to the desired subheadings. Then click "Add to Search Builder." Warning: Adding too many subheadings may lead to missing important articles.
  • MeSH/Subheading Combinations: You can manually add subheadings in the search box by using the format MeSH Term/Subheading, e.g. neoplasms/diet therapy. See abbreviations of MeSH subheadings, which can also be used. (MeSH Subheadings).
  • For a MeSH/Subheading combination, only one subheading at a time may be directly attached to a MeSH term. For example, a search of Hypertension with the subheadings Diagnosis or Drug Therapy will appear as Hypertension/diagnosis [mesh] OR Hypertension/drug therapy[mesh].
  • As with MeSH terms, PubMed search results, by default, include the more specific terms arranged beneath broader terms for the MeSH term and also includes the more specific terms arranged beneath broader subheadings.

4. How to Use Keywords

Automatic Term Mapping

  • PubMed uses Automatic Term Mapping (ATM) when you enter terms in the search box.
  • Automatic Term Mapping means that the search terms you type into the search box are automatically mapped to MeSH terms.
  • To see Automatic Term Mapping in action, click on the Details arrow in your Advanced > History and Search Details box.
  • Using quotes around a phrase or truncation turns off Automatic Term Mapping. The terms are instead searched exactly as entered, with no mapping applied.

Using Keywords

  • Keywords can be any words used to describe your idea or concept.
  • Keywords can be single words or phrases.
  • Use quotes around all phrases to ensure that the phrase is searched together.
  • For more ideas, visit the MeSH database and look at the entry terms listed in the MeSH record.
  • Also consider using synonyms, acroynyms, initialisms, variations in spelling, and other closely-related terms used interchangeably to describe the topic.

Keyword Generation

Keywords can be generated by:

  • browsing entry terms in PubMed's MeSH, and synonyms in Embase's Emtree to add additional keywords to a concept;
  • looking at a few key articles and seeing how the terminology is used; and by
  • doing a few preliminary searches and browsing the results to see how the terminology is used.

5. PubMed Pro Tips



You can use filters to narrow your search results by article type, text availability, publication date, species, language, sex, subject, journal category, and age. See more on Filters on PubMed's Help guide.

  • On the left side of the results are options to filter your search.
  • You can access additional filters through the link at the bottom of the filters bar.
  • "Text availability" is for users who are not affiliated with an institution. You do not need to limit by text availability since you have access to the JH Catalog and Interlibrary Loan.
  • Use filters cautiously. Limits other than date or language will limit your search to MeSH-indexed records only.
  • For example, if you would like to limit your results to "human studies," use the following search to exclude animal studies instead of using the "humans" limit from the search results page. Simply add this to the end of your search:
...NOT (animals[MeSH Terms] NOT humans[MeSH Terms])

Phrase Searching

Surround phrases with double quotes to search as a phrase to use a more specific search with more precision, and not as disparate words, which will result in a more sensitive search with higher recall. See more on Phrase Searching on PubMed's Help guide.

"hospital acquired infection" will return the phrase instead of hospital AND acquired AND infection


In PubMed you can use a * at the root of a word to find multiple endings.  For example:

arthroplast* will return arthroplasty, arthroplasties, arthroplastic, arthroplastics, etc.


mobili* will return mobility, mobilization, mobilisation, mobilize, etc.


Note: In New PubMed, you can now truncate a phrase inside quotes. "catheter infection*" will return catheter infections. See more on on Truncation on PubMed's Help guide.



Use search field tags to specify in which field the database queries for the search term. In PubMed, first type the search term and then the search field tag in brackets. e.g. Cardiology [tiab] searches for cardiology in the title and abstract.

  • [All Fields] or [all] – Untagged terms and terms tagged with [all fields] are processed using Automatic Term Mapping. Terms enclosed in double quotes or truncated will be searched in all fields and not processed using automatic term mapping.
  • [Text Words] or [tw] – Includes all words and numbers in the title, abstract, other abstract, MeSH terms, MeSH Subheadings, Publication Types, Substance Names, Personal Name as Subject, Corporate Author, Secondary Source, Comment/Correction Notes, and Other Terms.
  • [Title/Abstract] or [tiab] – Words and numbers included in the title, collection title, abstract, and other abstract of a citation. English language abstracts are taken directly from the published article. If an article does not have a published abstract, NLM does not create one.
  • NCBI explanation of Field Descriptions and Tags 

6. Combining Search Terms and Concepts

Boolean Operators

  • A comprehensive search of PubMed will include both controlled vocabulary (MeSH) and keyword terms.
  • Boolean operators are used to combine search terms. In PubMed, you can use the operators AND, OR, and NOT.
  • Go to the “Advanced Search” page to combine searches. This is where your search history is located during your search session.
  • Boolean operators MUST be used as upper case (AND, OR, NOT).
    • OR—use OR between similar keywords, like synonyms, acronyms, and variations in spelling within the same idea or concept
    • AND—use AND to link ideas and concepts where you want to see both ideas or concepts in your search results
    • NOT—use to exclude specific keywords from the search; however, you will want to use NOT with caution because you may end up missing something important

7. Saving Your Searches

To save searches and create alerts in PubMed, you must first create an account.

  • Create an NCBI account* by clicking on the "log in" button in the upper-right corner of the screen (sign up for a My NCBI account).
  • Once you complete a search, click on Create alert underneath the search box. From here you can create a search alert or save your search strategy.

*NLM changed the way you need to log into NCBI in 2021.  Information and updates can be found in NCBI Insights.

8. PDF Printable Handout

9. PubMed Practice

If you would like to practice comprehensive searching in PubMed, use the links below to access PubMed, and the three worksheets to achieve steps within the search process. See also the National Library of Medicine's Training Module on Using PubMed in Evidence-Based Practice.