The Lancet Formatting Requirements: Complete Author Guide

The Lancet uses a structured abstract that is among the most detailed of any top journal.

• Word limit: 300 words maximum
• Structure: Four mandatory headings:
• Background: State the purpose and context (2-3 sentences)
• Methods: Describe the study design, setting, participants, interventions, and primary outcomes
• Findings: Present the main results with effect sizes, confidence intervals, and p values
• Interpretation: Explain what the findings mean in clinical context; don't just restate results
• Funding: A separate line after Interpretation stating the funding source
• Citations: Not allowed
• Keywords: Not required. The Lancet assigns MeSH terms internally.

The Interpretation section is where many authors go wrong. The Lancet's editors specifically look for clinical implications, not a summary of results. "Our findings suggest that..." followed by a restatement of the numbers is insufficient. The Interpretation should tell clinicians what this means for patient care, policy, or future research direction.

The separate Funding line is a Lancet-specific requirement. It's not part of the 300-word count but must appear immediately after the abstract.

The Lancet's display item limit is firm at 5 for Articles.

Tables: The Lancet has specific table formatting rules that differ from most journals:

• Tables must be created in Word (or equivalent) using the table function, not as images
• No vertical lines in tables
• Horizontal lines only at the top, below the header row, and at the bottom
• Every column must have a header
• Footnotes use symbols in this order: *, dagger, double dagger, section sign
• Data in tables should include measures of variability (SD, IQR, 95% CI) and not just point estimates

Panel format for key findings: The Lancet uses a distinctive "Panel" format for boxes that highlight key information, definitions, or guidelines within the article body. Panels are numbered (Panel 1, Panel 2, etc.) and count toward the display item limit. They function like highlighted text boxes and are commonly used for inclusion/exclusion criteria, diagnostic algorithms, or practice points.

The Lancet uses Vancouver-style references, which are the standard for most medical journals.

In-text citations: Superscript numbers (e.g., "as reported previously^1"). Multiple references use commas without spaces (^1,2,3) or ranges (^1-5). Numbers are assigned in the order references first appear in the text.

Reference list format:

1 Author AB, Author CD, Author EF, et al. Title of article. Journal Abbrev Year; Volume: Pages.

Key formatting details:

• List up to 6 authors; if more, list the first 3 followed by "et al."
• No periods after author initials (e.g., "Smith AB" not "Smith A.B.")
• Journal names abbreviated per NLM/MEDLINE standards
• Year followed by semicolon, volume, colon, page range
• No issue numbers
• References to online-only articles should include the DOI
• Unpublished data and personal communications should be cited in the text, not in the reference list

The reference cap for Articles is 30. This is a hard limit, more strictly enforced than at Nature or Cell. At exactly 30 references, you need every citation to count. Cut references to general background that a Lancet reader would already know.

The Lancet's reference format doesn't include article titles for journal articles in some older style guides, but the current requirement is to include titles. Double-check this against the latest guidelines, as it changed in recent years.

The Lancet calls its supplementary content the "appendix" and treats it as a structured extension of the paper.

Appendix contents:

• Extended Methods (full protocol details, statistical analysis plan)
• Supplementary tables and figures (labeled as appendix tables/figures)
• Additional results not included in the main text
• Study protocols for clinical trials
• Search strategies for systematic reviews
• Sensitivity analyses and subgroup analyses

Formatting:

• The appendix must be compiled as a single PDF file
• It has its own internal pagination starting at page 1
• Figures and tables in the appendix are labeled sequentially (appendix figure 1, appendix table 1, etc.)
• The appendix goes through peer review alongside the main manuscript

Size and count: There's no formal limit on appendix length, but practical limits apply. Appendices for Lancet clinical trials often run 30-50 pages, including the full trial protocol. Systematic reviews may include appendix tables listing all included studies with extracted data.

Data sharing: The Lancet has a strong data sharing policy. Authors of clinical trials are required to share de-identified participant-level data upon reasonable request. The data sharing statement is a mandatory part of the manuscript and appears after the reference list.

A Lancet-specific detail: the appendix must reference the main text and vice versa. Any supplementary figure or table cited in the main text must include the label "(appendix p X)" where X is the page number in the appendix PDF. This cross-referencing is checked during production.

The Lancet requires a formal title page, which functions as the cover page.

Title page must include:

• Title: Concise and specific. The Lancet prefers titles that describe the study design (e.g., "Effect of X on Y in patients with Z: a randomised, double-blind, placebo-controlled trial"). Maximum 150 characters recommended.
• Author names and affiliations: Full names with department, institution, city, and country.
• Corresponding author: Full postal address, email, and telephone number.
• Word count: For the body text and separately for the abstract.
• Number of figures and tables: Listed explicitly on the title page.
• Number of references: Listed on the title page.

Additionally, The Lancet requires several declarations on a separate page:

• Contributors statement: Each author's specific contribution, using descriptive text.
• Declaration of interests: All financial and non-financial conflicts.
• Data sharing statement: Whether and how data will be shared.
• Acknowledgments: Including funding sources.

The Contributors statement is taken seriously. The Lancet requires that all authors meet ICMJE authorship criteria. Ghost authorship and honorary authorship are explicitly prohibited, and the editors investigate claims of inappropriate authorship.

This is where The Lancet stands apart from basic science journals like Nature and Cell. Reporting guideline compliance isn't just encouraged; it's a prerequisite for review.

The completed checklist must be submitted alongside the manuscript. Editors verify compliance before sending the paper for review. If the checklist indicates that required items are missing from the manuscript (e.g., a CONSORT flow diagram), the paper will be returned before review.

For clinical trials specifically, The Lancet requires:

• Prospective trial registration in a WHO-approved registry (ClinicalTrials.gov, ISRCTN, etc.)
• The registration number in the abstract and on the title page
• The full trial protocol submitted as part of the appendix
• An independent data monitoring committee for most trials
• A pre-specified statistical analysis plan

These are the details that catch even experienced clinical researchers:

Panel format. The Lancet uses numbered Panels (Panel 1, Panel 2) for highlighted boxes within the text. These are used for practice guidelines, diagnostic criteria, inclusion/exclusion criteria, or key clinical messages. They count toward the 5-item display limit. Don't confuse Panels with figure panels (A, B, C within a figure).

Findings, not Results. The Lancet uses "Findings" as the heading for the results section in the abstract and often in the main text. Using "Results" instead is technically acceptable in the main text, but using "Findings" in the structured abstract is mandatory.

Interpretation, not Conclusions. Similarly, the abstract uses "Interpretation" not "Discussion" or "Conclusions." This isn't cosmetic. The Lancet's editors view "Interpretation" as requiring more than a summary. It demands clinical judgment about what the findings mean.

Study registration display. For clinical trials, the registration number and registry name must appear at the end of the abstract, before the Funding line. The format is: "Registration: ClinicalTrials.gov, NCT01234567."

SI units. The Lancet requires SI units for all laboratory values, with conventional units in parentheses if desired. This is the opposite of many US-based journals (like NEJM) that prefer conventional units first.

Drug names. Use generic (non-proprietary) names throughout. Brand names can be mentioned once in parentheses at first use but shouldn't appear in the title or abstract.

Decimals and numbers. The Lancet uses a middle dot (interpunct) as the decimal separator in some contexts (Lancet house style), though standard decimal points are accepted in submitted manuscripts. Numbers less than 10 should be spelled out in running text unless they're measurements.

Figures must be interpretable in grayscale. While color is free, The Lancet requires that figures remain interpretable without color (for readers who print in black and white or have color vision deficiencies). Use patterns, different line styles, or redundant coding in addition to color.

1. Structured abstract with Funding line. The Funding line is separate from the abstract but must appear directly below it. It's not part of the 300-word count.

1. CONSORT/STROBE/PRISMA flow diagrams. These count as one of your 5 display items. Plan accordingly. A clinical trial with a CONSORT flow diagram only has 4 remaining slots for figures and tables.

1. Appendix cross-referencing. Main text citations to appendix material must include the appendix page number: "(appendix p 12)." Production will flag missing page numbers.

1. Contributors vs. Acknowledgments. Contributors are authors. Acknowledgments are non-authors who assisted. Don't list authors in Acknowledgments or non-authors in Contributors.

1. Data sharing statement. Mandatory for all Articles. Must specify what data will be shared, with whom, for what purpose, and by what mechanism.