Convert NBIB to BIB

PubMed exports selected references as .nbib, while LaTeX, Overleaf, and many reference managers use .bib BibTeX databases. Converting the records makes them editable and usable with BibTeX or biblatex citation workflows.

What the NBIB format is

NBIB is PubMed's tagged citation format, also called MEDLINE or PubMed text format. It is a plain-text record format with labeled fields such as PMID-, TI -, AU -, JT -, DP -, VI -, IP -, PG -, and LID - for identifiers such as DOIs.

PubMed creates an NBIB file after selecting records and choosing Send to → Citation manager → Create file. NCBI users, libraries, and applications such as Zotero and EndNote use the format to exchange bibliographic metadata. An NBIB file can be opened as plain text, but its tagged lines are not directly valid BibTeX.

What the BIB format is

A .bib file is usually a BibTeX or BibLaTeX database containing entries such as @article{smith2024, ...}. BibTeX, BibLaTeX with Biber, JabRef, Zotero, Overleaf, and many LaTeX editors can read it.

BibTeX stores structured fields including authors, title, journal, year, volume, pages, DOI, URL, abstract, and a citation key. The plain-text format is searchable, editable, portable, and separate from the document that cites it. The conversion can preserve metadata, but it cannot add a missing full-text article or attachment.

Convert with Zotero

1. Install Zotero for Windows, macOS, or Linux from the official Zotero website.
2. Open File → Import, select the NBIB file, and choose the MEDLINE or PubMed import option if Zotero asks for a format. Use All files in the file picker if .nbib is hidden.
3. Check the imported records, especially author names, titles, publication dates, page ranges, PMIDs, and DOIs.
4. Select the required items or collection, then choose File → Export Library or right-click the selection and choose Export Items.
5. Choose BibTeX or BibLaTeX, select any note or file options required by the workflow, and save the export with a .bib extension.

Zotero is usually the simplest local method because it parses tagged PubMed fields before exporting them. For missing metadata, use Zotero's Add Item by Identifier with the PMID or DOI, then compare the replacement record with the PubMed source before exporting. The Better BibTeX extension adds configurable, repeatable citation keys and automatic export, but it is optional.

Use Bibutils for batch conversion

Bibutils is suitable for scripted or large-scale local conversion. Its MEDLINE-to-XML and XML-to-BibTeX stages can be used as a pipeline:

med2xml references.nbib | xml2bib > references.bib

Install Bibutils through the operating system's package manager or its official distribution. Check med2xml --help if the installed build requires explicit input and output arguments. Bibutils may map fewer PubMed-specific fields than Zotero, so inspect the generated entries before using them.

Online options for small, non-sensitive sets

For a small list of references, ZoteroBib or Paperpile's PMID-to-BibTeX web tool can look up PMIDs and produce BibTeX without requiring a local application. These services generally accept PMIDs or identifiers rather than converting an uploaded NBIB file; paste the identifiers, export BibTeX, and verify the results. Do not upload private, unpublished, or confidential bibliographies when a local conversion is acceptable.

Check the exported records

• Some NBIB records omit DOI, issue, page, abstract, or complete publication-date fields. A DOI or PMID lookup can fill gaps, but retrieved metadata still needs comparison with the source record.
• PubMed's author formatting can produce incorrect personal or corporate authors after conversion. Put a corporate author in extra braces, for example author = {{World Health Organization}}, and check surname, initials, and author order.
• Protect capitalization that must remain unchanged, such as gene symbols, acronyms, and proper names, with BibTeX braces: title = {Effects of {DNA} repair}.
• Unicode characters, en dashes, subtitles, accented names, and non-Latin scripts may require UTF-8 support in the LaTeX engine, bibliography processor, and editor. Use pdflatex with appropriate encoding settings or a Unicode engine such as XeLaTeX or LuaLaTeX.
• Different exporters generate different citation keys. Changing a key after inserting citations can break references in existing LaTeX files; use stable keys before writing citations.
• Preserve the PMID or DOI in the exported entry when possible. These identifiers provide a reliable way to locate and correct a record later.