JCI Formatting Requirements: Complete Author Guide

JCI uses an unstructured abstract for all article types that require one. There are no subheadings, no Background/Methods/Results/Conclusions structure.

• Word limit: 200 words maximum for Research Articles
• Structure: Single paragraph, unstructured
• Citations: Not permitted in the abstract
• Keywords: JCI doesn't require author-supplied keywords in the abstract or frontmatter

The 200-word cap is tight. You need to state the problem, describe the approach briefly, and present the main findings. Don't spend 40 words on background context that any reader of JCI already knows. Start with the specific gap or question.

One formatting detail that trips people up: JCI's abstract should not include abbreviations that aren't universally recognized in biomedical research. If you use an abbreviation, define it on first use within the abstract, and then define it again on first use in the main text. The abstract and body are treated as separate documents.

JCI allows up to 8 main figures in a Research Article. Tables are counted separately from figures, which is different from journals that combine figures and tables into a single "display items" limit.

Figure specifications:

Table requirements:

• Tables must be created in Word using the table function, not pasted as images
• Every column needs a header
• Use horizontal rules at the top, bottom, and below column headers only
• No vertical rules
• Footnotes use lowercase superscript letters (a, b, c)
• P values should be reported to 2-3 decimal places

Supplemental figures: JCI places no hard cap on supplemental figure count, but editors and reviewers will push back on excessive supplemental data that should either be in the main paper or cut entirely. A common range is 5-15 supplemental figures for a typical Research Article.

Multi-panel figures are the norm at JCI. A single figure with panels A through H is common, and it counts as one figure toward your limit of 8. Use this to your advantage. Group related experiments into composite figures rather than spreading them across separate numbered figures.

One JCI-specific detail: graphical abstracts aren't required or standard at JCI. Don't create one unless the journal specifically requests it during production, which is rare.

JCI uses a numbered sequential citation system. References are cited as superscript numbers in the text and listed numerically in the reference list.

In-text citations: Superscript numbers (e.g., "as demonstrated previously^1,2"). Numbers are assigned in the order references first appear in the text. Multiple citations are separated by commas with no spaces (^3,4,5 or ^3-5 for consecutive numbers).

Reference list format:

1. Smith AB, Jones CD, Williams EF. Title of the article in sentence case. J Clin Invest. 2025;135(4):e12345.

Key formatting details:

• Author names: Last name followed by initials with no periods (e.g., "Smith AB")
• List all authors when there are 10 or fewer. For 11 or more, list the first 10 followed by "et al"
• Journal names follow standard NLM abbreviations
• Volume numbers are not bolded
• Include issue numbers in parentheses
• Page numbers or article IDs are required
• DOIs should be included when available

JCI doesn't enforce a hard reference cap for Research Articles, but most published papers fall in the 40-60 reference range. Reviews can go higher. If you're at 80+ references for a Research Article, that's a signal your paper might be trying to do too much.

JCI's own abbreviation: When citing JCI itself, use "J Clin Invest" as the abbreviated journal name.

JCI calls supplementary content "Supplemental Material" (not "Supplementary" with a y, which is a small but notable style choice). Supplemental data is peer-reviewed and published alongside the article.

Supplemental material should be organized as:

1. Supplemental Methods: Extended methodological details that don't fit in the main Methods section
2. Supplemental Figures: Numbered sequentially (Supplemental Figure 1, Supplemental Figure 2, etc.)
3. Supplemental Tables: Numbered sequentially, preferably in Excel format for data tables
4. Supplemental Data: Raw datasets, code, or other supporting files

All supplemental material should be compiled into a single PDF for review, with individual source files uploaded separately. Videos and large datasets are uploaded as standalone files.

There's no formal page limit for supplemental material, but JCI editors have made it clear in editorial statements that the supplement shouldn't become a second paper. If your supplemental data is longer than your main manuscript, reconsider whether some of that data belongs in the main figures or whether it's truly necessary.

Data deposition: JCI requires that all sequencing data, microarray data, proteomics data, and structural data be deposited in appropriate public repositories (GEO, PRIDE, PDB, etc.) with accession numbers cited in the manuscript.

JCI requires both a title page (as the first page of your manuscript) and a cover letter (submitted separately).

Title page must include:

• Full title (no abbreviations)
• Short running title (60 characters max)
• All author names with degrees and affiliations
• Corresponding author contact details
• Conflict of interest statement
• Total word count, figure count, and table count

Cover letter should address:

• Why the work fits JCI's scope (translational biomedical research)
• What's new compared to existing literature
• Any potential conflicts of interest
• Suggested reviewers (at least 3) and excluded reviewers (optional)

JCI's editorial scope is translational medicine. Basic science papers without a clear path to clinical relevance don't fit, and the cover letter is where you establish that connection. Don't just describe what you found. Explain what it means for understanding or treating disease.

These are the details that experienced JCI authors know but that first-time submitters often miss:

Methods are in the main text. Unlike Nature, Cell, and Science, JCI keeps the Methods section in the standard IMRAD position within the body of the paper. The order is Introduction, Results, Discussion, Methods. Some authors place Methods before Results, and JCI accepts either order, but Results-first is more common in published papers.

No structured significance statement. Unlike PNAS, JCI doesn't require a separate lay-audience summary or significance statement. The abstract serves this purpose.

Author contributions statement. Required for all Research Articles. Must list each author's specific contributions. JCI uses free-text format, not CRediT taxonomy. This appears at the end of the manuscript before references.

Conflict of interest statement. Mandatory, even if there are no conflicts to declare. Must appear on the title page.

Ethics statements. Human subjects research requires IRB approval numbers and informed consent language. Animal studies require IACUC approval details. These go in the Methods section, not in a separate section.

ORCID iDs. The corresponding author must provide an ORCID iD. Co-authors are encouraged but not required.

Abbreviation use. JCI follows the convention of defining abbreviations at first use in both the abstract and the body text separately. Commonly accepted abbreviations (DNA, RNA, PCR, ELISA) don't need definition.

Title formatting. JCI titles should be specific and informative. Questions in titles are allowed but uncommon. Colons are acceptable. The journal doesn't enforce a strict character limit, but most published titles fall between 80 and 150 characters.

1. Line numbering is required. Every page of the manuscript must have continuous line numbers. This is essential for reviewers and editors to reference specific sections in their comments. Word can add these automatically through Layout > Line Numbers > Continuous.

1. Double spacing. The entire manuscript must be double-spaced, including references and figure legends. Single-spaced submissions will be returned.

1. Page numbers. Required on every page, starting from the title page.

1. Figure legends go at the end. Figure legends should appear after the reference list, not under each figure. Figures themselves are uploaded as separate files.

1. Units. Use SI units throughout. Express concentrations in molar terms (mM, not mg/mL) when possible. Temperature in Celsius.

1. Statistical reporting. All statistical tests must be identified in the Methods and figure legends. Report exact P values rather than thresholds (P = 0.003, not P < 0.05). Include sample sizes and measures of variance.

JCI's formatting requirements are more forgiving than many top-tier journals. The 5,000-word limit gives you room to tell a complete story, the 8-figure cap is generous, and the IMRAD structure with in-body Methods is standard enough that most authors don't need to restructure their manuscripts.

The bigger challenge at JCI is meeting the editorial bar for translational impact. If you want to check whether your manuscript is ready for a high-impact submission, run a free formatting and readiness scan to catch the technical issues that lead to desk rejection.

For the most current author guidelines, check JCI's instructions for authors. Templates and checklist documents are available through that page.

If you're also evaluating journal fit, our guides on JCI impact factor and PNAS formatting requirements cover journals with a similar translational scope.