For many searches, it is not necessary to use special tags or syntax. PubMed uses multiple tools to help you find relevant results.
- Identify the key concepts for your search.
- Enter the terms (or key concepts) in the search box.
- Press the Enter key or click Search.
There are 3 ways to save search results:
- Citations can be saved temporarily to the Clipboard. The Clipboard holds up to 500 items from one or more searches. Items saved to the Clipboard expire after 8 hours of inactivity.
- Save citations indefinitely using My NCBI Collections. Collections can be made public to share with others. To save results, you must be logged into your My NCBI account Read more about Collections.
- Citations can also be saved as a text file (.txt). Read more about saving as a text file.
The Best Match sort order is based on an algorithm that analyzes 150 signals that are helpful for finding best matching results in each PubMed citation found with your search terms.
There are 5 sort order options:
- Best Match
- Most Recent
- Publication Date
- First Author
- Journal
As of February 2023, searchers can identify how PubMed citations were indexed by appending one of these 3 search strings on the right to their search.
- Automated: indexingmethod_automated
- Curated: indexingmethod_curated
- Fully human indexed: medline[sb] NOT (indexingmethod_curated OR indexingmethod_automated
Learn more about the 3 indexing methods used for newly added citations.
There are several ways to search for a specific author. You may need to use more than one strategy to find all citations by the author you are searching for.
NLM suggests that you enter the author’s last name and initials without punctuation in the search box and click Search.
A list of journals included in PubMed is available by FTP.
Enter one of the following in the search box:
- full journal title (e.g., molecular biology of the cell)
- MEDLINE title abbreviation (e.g., mol biol cell)
- ISSN number, a standardized international code (e.g., 1059-1524)
You can search for a term in a specific field by including a search field tag after the term.
For example, UCLA [ad] will search for the term “UCLA” in the affiliation field only.
The MEDLINE/PubMed Data Element table describes the major fields for PubMed MEDLINE records.
- Not all fields will appear in every record.
Only some of the elements on the field list are searchable fields in PubMed.
Sometimes a search yields too many results.
To limit the number of search results:
- Replace general search terms with more specific ones (e.g., low back pain instead of back pain).
- Include additional terms in your query.
- Use the sidebar filters to restrict results by publication date, full text availability, article type, and more.
You may receive too few results for a number of reasons (new concept, restricted to MeSH, filters applied, etc.).
- Remove extraneous or specific terms from the search box.
- Try using alternative terms to describe the concepts you are searching for.
On the abstract page for a citation, see the Similar Articles section for a pre-calculated set of additional PubMed citations closely related to that article.
You can use filters to narrow your search results by article type, text availability, publication date, species, article language, sex, age, and other.
Read more about how to filter by:
To apply a filter:
- Run a search in PubMed.
- Click the filter you would like to activate from the left-hand sidebar. A check mark will appear next to the activated filter(s).
Subsequent searches will be filtered until the selected filters are turned off, or until your browser data is cleared.
PubMed provides several different methods to adjust the date to meet your search criteria.
You can use proximity searching to search for multiple terms appearing in any order within a specified distance of one another in the [Title], [Title/Abstract], or [Affiliation] fields.
To create a proximity search in PubMed, enter your terms using the following format:
"search terms"[field:~N]
- Results will include your quoted terms in any order.
- Automatic Term Mapping is not applied to the quoted terms.
- Proximity searching is not compatible with wildcards (*).
- You can combine proximity searches with other terms using Boolean operators; for example, "hip pain"[Title:~4] AND stretching
- Booleans and stopwords included in quoted terms for proximity search are searched like regular keywords.
You can search by type of empirical method used.
- The Study Characteristics [PT] field describes the type of empirical method used in the study.
- You can view the full MeSH hierarchy for this branch.
- You can find a complete list of Publication Types in PubMed Help
This strategy is intended to retrieve citations to systematic reviews in PubMed and encompasses citations assigned the "Systematic Review" publication type during MEDLINE indexing; citations that have not yet completed MEDLINE indexing; and non-MEDLINE citations.
Example: exercise hypertension AND systematic [sb]
The Browser is an alternative search interface for MeSH vocabulary that allows users to search directly for MeSH terms and conduct text word searches of various fields of the records.
- There’s a browser for the current year MeSH vocabulary and one previous year.
- The files are updated each week day Monday-Friday by 8AM EST.
This tool assists with term generation and can automatically identify relevant MeSH terms from text that is input by the user.
MeSH on Demand suggested MeSH vocabulary is machine-generated by NLM’s Medical Text Identifier (MTI) and DOES NOT reflect any human review. MTI may recommend MeSH Terms not explicitly found in the text.
Read more about MeSH on Demand.
Associated data links are included on the abstract page of a citation and can be found quickly via the navigation links on the right side of the page. The Associated data section only appears for citations with one or more of these data.
- Users can find citations with associated data by searching for data[filter] or by applying the associated data filter from the left side bar to their search results.
- To find citations in PubMed that link back to clinical trials, use the following format to search in PubMed: clinicaltrials.gov[si] Vertigo
Your PubMed search history appears on the Advanced Search page under History.
To download, go to the Advanced page, click Download to generate a CSV file of current History items.
Please note, Microsoft Excel is typically unable to display or print more than a maximum of 1024 characters in a cell; therefore, you may want to open the CSV file with a text editor to display your complete list of searches.
Citations can be exported into citation management software.
Use Send to: Citation Manager to export citations as an .nbib file that can be used by many citation management programs.
Email yourself or your collaborators citations or get a permalink to bookmark or share your search results.
- Use the check boxes to select citations from your search results or Clipboard. You may move to other pages and continue your selections. You may also choose to email all citations shown on the page without making any selections. From the PubMed Results Page, select Email. Read more about emailing citations.
- Your citations will be sent from the NCBI automatic mail server with the sender's email address [nobody@ncbi.nlm.nih.gov]. Do not reply to this message, as this is not a functioning customer service email address and is not monitored.
Obtain a permalink/URL to bookmark or share your search. A permalink is a permanent link that will constantly direct you to an article or an online resource.
- To get the URL for an individual citation, copy the permalink for the citation under "Share."
- To get the URL for your search results, copy the URL from your web browser's address bar or bookmark the URL using your web browser's bookmark function.
- Create a URL manually
Use the print function of your web browser.
To print citations from different searches, save the citations to PubMed’s Clipboard, and then print.
Citing sources is important because it gives credit to the people whose ideas or words are being used. Citations can also make work more credible.
The Cite button makes it easy to retrieve styled citations that you can copy and paste into a document or download as an .nbib file to use with your reference manager software. Capitalization of article titles and other citation elements should be checked for compliance with a particular reference style when required.
Searching clinical trials registers is considered best practice for systematic reviews. Including eligible studies with unpublished data in systematic reviews helps synthesize the complete body of evidence and mitigates publication bias. (Hunter, 2022)
As the world’s largest clinical trials register, ClincalTrials.gov is a key resource for identifying relevant research studies with unpublished results.
Two search interfaces are available in ClinicalTrials.gov.
Review this information if you are new to searching ClinicalTrials.gov or need a fresher on using Basic Search.
Review this information if you are new to searching ClinicalTrials.gov or need a fresher on using Basic Search.
The terms you enter are not searched throughout the entire study record; the areas that are searched depend on which input field you use.
Search Areas refer to the specific parts of a study record that are searched based on the input fields.
Some Search Areas include multiple weighted study fields that can be searched simultaneously. For example, if you enter terms in the Condition/disease input field, the search will cover seven different data fields. Other Search Areas may consist of just a single data field, such as Acronym or Brief Title.
Detailed information can be found here:
See also, Using Expert Search for complex searches, for more information on using search areas when conducting searches and to learn how to build detailed searches on ClinicalTrials.gov.
ClinicalTrials.gov does not perform any indexing of study records, and does not apply Medical Subject Headings (MeSH) terms to submitted studies.
All MeSH terms and keywords included in the study record are supplied by research teams when they register the study.
ClinicalTrials.gov’s Protocol Registration Quality Control Review Criteria provides the following guidance to research teams:
Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study
- Definition: The name(s) of the disease(s) or condition(s) studied in the clinical study, or the focus of the clinical study.
- Use, if available, appropriate descriptors from MeSH or terms from another vocabulary, such as the Systematized Nomenclature of Medicine—Clinical Terms (SNOMED CT), that has been mapped to MeSH within the Unified Medical Language System (UMLS) Metathesaurus.
Keywords
- Definition: Words or phrases that best describe the protocol.
- Keywords help users find studies in the database. Use MeSH-controlled vocabulary terms where appropriate. Be as specific and precise as possible. Avoid acronyms and abbreviations.
No ontologies are used in any other search field.
Expert Search provides an alternative search interface that is more conducive to using complex search expressions.
Expert Search allows you to construct, perform, edit, and view complex search queries. Focusing your search in this way can deliver more precise results. The Expert Search page includes a chronological Search Query history table for tracking, saving, and editing up to ten successful search queries.
Expert Search is available from several locations in ClinicalTrials.gov.
- The top right corner of the Focus Your Search box on the homepage
- The menu under Find Studies
- A link under Find Studies on the Site Map
Complex search strings can also be constructed in the Other terms input field from the Focus Your Search box on the homepage.
Complex searches may be constructed in either the Other terms input field from the Focus Your Search box on the homepage, or by using Expert Search. There is no difference in what can be inputted or in the resulting search results.
The following information explains the use of search operators, search terms, and search expressions that used to build an advanced search.
- Search operators: affect which studies are returned and how they are ordered in retrieval sets
- Search terms: words or phrases that must appear as values in the study records returned by the search
- Search expressions: search expressions consist of a sequence of terms and operators
You may want to test a search string that has been run in a bibliographic database like PubMed to see if it retrieves previously identified eligible studies.
The search string will need to be translated to conform to search expressions and syntax accepted by ClinicalTrials.gov., and should be entered in the Other terms input field.
Search string length limitations are based on the URL length restrictions of your browser or user agent.
ClinicalTrials.gov recommends searching on Safari for long search strings.
Consider the following options to refine your search strategy.
- Focus your search by adding filters. Review Focus Your Search Menu and Special instructions for using certain search filters.
- Turn off the inclusion of synonyms. By default, ClinicalTrials.gov automatically includes synonyms for search terms entered in the Condition/disease input field. The automatic inclusion of synonyms may be turned off by typing the command, EXPANSION[Term]"keyword or phrase" in the Condition/diseaseinput field.
Review this information to learn how to search for clinical studies that have results posted on ClinicalTrials.gov.
- Quick guide to searching for studies with results
- How to add the results filter from the Search results page
Results include information about the study's participant flow, baseline characteristics, outcome measures, and adverse events (including serious adverse events).
Note that not all studies have results. This may be because a study isn't done or the deadline for submitting results has not passed. Some studies are not required to submit results.
Including eligible studies with unpublished results in systematic reviews helps synthesize the complete body of evidence and mitigates publication bias. (Hunter, 2022)
Follow these steps to narrow your search results to studies that have results posted but do not have any publications relating to those results entered by the data submitters.
- Enter AREA[ReferenceType]NOT RESULT in the Other terms input field, and apply the Study with Results filter.
- For each study record, open the Results Posted tab and carefully review the Publications section.
- The search may retrieve studies with other types of submitted publications, such as those related to the study background or protocol.
- The search may retrieve studies with research results publications if study data submitters have not updated the study record to indicate a publication about the results exists.
- The search may also retrieve derived references that are auto-indexed from PubMed. These auto-indexed publications may or may not be related to study results. You will need to check the abstract and/or the full-text of the article to confirm this.
The default order for the display of search results is relevancy.
- Relevance is determined by best match to search terms and synonyms.
- Proximity is also considered if a location has been entered.
The display order may be changed to newest first by clicking on the “Sort studies by” drop down menu on the Search Results page and selecting Newest First.
The retrieved order may also be sorted by any numeric or date input field. These changes may be made by using StudyFirstPostDate, or any other date or numeric field from the Study Data Structure, on the /studies API endpoint on the ClinicalTrials.gov API page using the sort filter.
Lastly, you can change the number of studies you see on each page.
Learn about the three main parts of the Search Results page and discover helpful features:
Review the following information to learn how to read and understand a study record.
Review this information to learn how to read study results in records posted on ClinicalTrials.gov.
- Quick guide to reading study results
- Where to find results in a study record
- How to read each section of the study results
Results include information about the study’s participant flow, baseline characteristics, outcome measures, and adverse events (including serious adverse events).
The study results provided in a ClinicalTrials.gov record are not meant to be interpreted without help from an expert. Interpreting study results is complex because many factors can influence their meaning. For more information about the results of a specific study, contact the results point of contact found in the Results Overview section.
Review this information to learn how to download information about some or all of the studies shown in your search results, or the information from a single study.
- Select studies to download or save
- Download studies
- Download study information from the Search Results list
- Download information from a single study
The maximum number of results that can be downloaded from the search results is 10,000. Larger datasets can be pulled from the API.
Available file formats for downloading now include RIS, the preferred choice for systematic reviews.
Additional file formats are CSV, JSON, FHIR JSON, and zipped JSON.
Basic Search
No options are currently available to save search strategies and history within the Basic Search interface of ClinicalTrials.gov. However, the registry does offer Really Simple Syndication (RSS) feeds and the option to save selected studies for easy retrieval.
Review this information to learn about RSS.
- Create an RSS Feed
- Subscribe to a Feed
- Bookmark Search Results pages as an alternative to RSS feed
- Add studies to My Saved Studies
Expert Search
Expert Search includes a chronological Search Query history table that enables you to save up to ten successful search queries.
There is no time limit associated with persistence of search queries in the history table. Persistence of the entries in this table are tied to your browser and are only disrupted when you delete your browser data associated with ClinicalTrials.gov., you use either a different browser or browser user profile, or you have ten search queries in history and execute a unique 11th search query (in which case, the oldest entry in search query history will be removed).
RSS feeds can provide updates on all recently added or modified study records on ClinicalTrials.gov, or updates to the results of a specific search. The RSS feed will automatically list additions and updates in either your Internet browser or a feed reader.
Review this information to learn about RSS.
- Create an RSS feed
- Subscribe to a feed
- Bookmark Search Results pages as an alternative to RSS feed
To keep abreast of updates to features and functionality on ClinicalTrials.gov:
- Review News and Updates
- Review Release Notes
- Sign up for the ClinicalTrials.gov newsletter, Hot Off the PRS.
Use this two-page guide for quick reference when searching ClinicalTrials.gov.