PubMed is one of the largest online indexes of biomedical literature from MEDLINE, with over 33 million citations. It is a very valuable resource for anyone trying to find medical literature on a given topic. However, with 33 million citations (and counting), searching PubMed can be daunting. Over the last 20 years there has been very large bodies of works published on diabetes (over 40,000 in 2019 alone) and complementary and alternative medicine (CAM). In 2021, the National Library of Medicine merged these collections which makes it easier to find articles that cross topics, but doesn’t necessarily make it easier to narrow down your results. For example: a basic search for the term “diabetes” returns over 864,500 articles today.
Halebee prepared this guide to provide tips and tricks to making the search work for you. The first goal is to identify the right search terms to use. The second goal is to search the collections that will give you results you are looking for. Let’s get started!
Launch PubMed.gov website
Click here to load the website in another tab.
Basic searches
Just like Google, you can type a search term(s) into the box and get results. Unlike Google, PubMed does not chunk up the results into bite-sized pages. In order to narrow these 864,590 search results into something manageable, you will want to follow these three steps:
- Use more key words in your search. For example: “diabetes and herbal medicine”
- Use the filters to narrow the search. For example: use the slider to change the date range to 2000-2022
- Try changing the sorting mechanism. Best match works pretty well, but you may be better off looking for the most recent results.
By following these steps, I can get the number of results down to 3,262. Still a lot of papers, but I can do more to narrow the results!
Using filters
To narrow my search down further, I will check the box for “free full text” which means that I can read & download them for free [see screenshot above]. I will also use the filter to select “clinical trial” and “randomized controlled trial”. These filters will help me find papers that include only human participants. Now my results list is down to 185 papers! I can sort by the most recently published to see the newest research on this topic.
MeSH
It can be hard to decide on what term or terms to use in the search box. In the above example, I searched for the phrase “herbal medicine”. But what if I used the term “herbs” or “herbal supplement”? Which is better? That is where MeSH comes in! MeSH stands for medical subject headings. You can search through MeSH to find the search term that will give you the broadest (largest) set of results or to narrow it down. Let’s look at the MeSH term “diabetes”.
In PubMed, the term “diabetes” is actually expanded for you to the following:
“diabetes mellitus”[MeSH Terms] OR “diabetes insipidus”[MeSH Terms] OR diabetes[Text Word]
If I want to broaden the search I could try the terms “glucose metabolism disorders” or “endocrine system diseases”. [higher in hierarchy]
If I want to narrow the search I could try the terms “diabetes mellitus, type 2” or “diabetic neuropathies”. [lower in hierarchy]
Putting it all together
Searching for the terms “diabetes mellitus, type 2 and herbal medicine” for the last 20 years returns 29 results. If I narrow that down to clinical trials and free full text papers, I end up with only 4 results. This is a much easier paper set to review than 864,500. Amazing!
