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Unified Medical Language System® (UMLS®)

MeSH Source Information

Web site:

The Medical Subject Headings (MeSH®) are developed and maintained by the U.S. National Library of Medicine (NLM).

The MeSH thesaurus is a controlled vocabulary used for indexing, cataloging, and searching for biomedical and health-related information and documents. It enables retrieval systems, such as PubMed, to provide subject searching of data.

MeSH consists of sets of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.

The three basic types of MeSH records are Descriptors, Qualifiers (subheadings), and Supplementary Concept Records.

MeSH has over 27,000 Descriptors; 83 topical Qualifiers; more than 232,000 Supplementary Concept Records; and over 87,000 entry terms.

MeSH is continually updated by NLM health science subject specialists. New terms from scientific literature and research can be recommended for addition to MeSH.

MeSH is also included in RxNorm.

Metathesaurus Scope
The Metathesaurus also includes the following MeSH translations:

  1. Croatian
  2. Czech
  3. Dutch
  4. Finnish
  5. French
  6. German
  7. Italian
  8. Japanese
  9. Latvian
  10. Norwegian
  11. Polish
  12. Portuguese
  13. Russian
  14. Spanish
  15. Swedish

The MeSH vocabulary is designed for use by NLM for indexing and searching the MEDLINE database of journal citations and cataloging the NLM collection.

MeSH is used by indexers, subject catalogers, online searchers, and in retrieval systems.

Update Frequency
A revised MeSH vocabulary is released annually; Descriptors and Qualifiers are updated annually while Supplementary Concept Records are updated continuously.

Metathesaurus Update Frequency
MeSH is an updated source in each Metathesaurus release. Descriptor and Qualifier changes appear in the November release while Supplementary Concept Record changes appear in each release.

Sites Consulted

  1. Fact Sheets [Internet]. Bethesda (MD): National Library of Medicine (US); 2001 Jan 01 [reviewed 2008 Aug 05; updated 2008 Aug 05]. Medical Subject Headings (MeSH®); [reviewed 2011 Jan 06; updated 2011 Jan 06; cited 2012 May 15]. Available from:
  2. Medical Subject Headings [Internet]. Bethesda (MD): National Library of Medicine (US); 1999 September 01 [reviewed 2011 Oct 28; updated 2011 Oct 28]. Preface; 2008 Oct 07 [updated 2007 Oct 08; cited 2012 May 15]. Available from:; MeSH record types:; Use of MeSH in online retrieval: