This can be tricky.
If you are using an article citation database then the content of the database may be entirely "peer reviewed" or you may have to select a limiter to remove content that does not meet this threshold.
- Scopus results should be entirely from the peer reviewed journal literature. Note: book content and conference citations are included in your overall results.
- PubMed - most journals are peer reviewed. Please note, the free articles in the PubMed Central repository are not the same thing as PubMed. And there are concerns that lower quality or predatory journals *may* be included in this journal repository, which is linked to PubMed.
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- EBSCOhost or Proquest databases - limit your search results to "peer review"
If you are using Google Scholar, the only way to verify may be to go to publishers website to read about their submission requirements and review process.
To learn more about Peer Review, please see the library's guide.