These articles should report original research studies that are relevant to clinical medicine in a way that is accessible to readers of a general journal.

To find out more about the kind of research we give priority to, and what services we offer to authors of research please read this editorial: Why submit your research to the BMJ?

Open access

The full text of every research article published in the BMJ is immediately accessible on bmj.com to everyone at no charge. The full text of all research articles is also sent, without further intervention from the author, to PubMed Central, the National Library of Medicine's full text archive, which makes it fully accessible without delay. This means that the BMJ immediately fulfils the requirements of the US National Institutes of Health, the UK Medical Research Council, the Wellcome Trust, and other funding bodies to make publicly funded research freely available to all.

Here is all the information you need to prepare and submit your research article:

Overall style

Original research articles should follow the IMRaD style (introduction, methods, results and discussion) and should have a structured abstract and a structured discussion.

No word limit

We do not set fixed limits for the length of BMJ research articles and can be flexible. We produce abridged versions of research articles in the printed BMJ while publishing their full versions on bmj.com. Nonetheless, please try to make your article concise and make every word count. Think hard about what really needs to be in the paper to get your message across accurately and what can be left out.

What other information do we need?

Please see our general requirements for all BMJ manuscripts which give full details of what you should include with all manuscripts. For original research articles in particular, please note that we need, as appropriate:

In the manuscript:

• a competing interest statement -  either a statement describing the interests of all authors or a declaration "All authors declare that the answer to the questions on your competing interest form are all No and therefore have nothing to declare". We no longer need to see a hard copy of the signed form.
• details of contributors and the name of the guarantor
• a statement in the manuscript that any identifiable patients have provided their signed consent to publication. Please submit, as a supplemental file, the signed BMJ patient consent form giving consent to publication in the BMJ of any information about identifiable individual patients. Publication of any personal information about a patient in the BMJ, for example in a case report or clinical photograph, will normally require the signed consent of the patient.
• details of ethics approval (or a statement that it was not required)
• details of funding
• description of the role of the study sponsor(s), if any, in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication
• statement of the independence of researchers from funders  
• trial registration number and name of register for a clinical trial – in the last line of the structured abstract
• for a clinical guidelines article explicit statements of the quality of evidence and strength of recommendations, preferably using the GRADE system (we encourage but do not insist on this).

As supplemental files:

• the appropriate CONSORT checklist, structured abstract, and flowchart for a randomised controlled trial (CONSORT has several extension statements, eg for cluster RCTs)
• the original protocol for a clinical trial
• QUOROM checklist and flowchart for a systematic review
• MOOSE checklist and flowchart for a meta-analysis of observational studies
• STARD checklist and flowchart for a study of diagnostic accuracy
• STROBE checklist for an observational study
• BMJ health economics checklist

In the cover letter:

• assurance that a clinical trial funded by a pharmaceutical company follows the guidelines on good publication practice and that any article written by a professional medical writer follows the guidelines by the European Medical Writers' Association on the role of medical writers

To find research reporting guidelines and statements such as CONSORT you may find it easiest to go to the website of the EQUATOR network. This network seeks to improve the quality of scientific publications by promoting transparent and accurate reporting of health research.

Summary statistics to clarify your message

We do want your piece to be easy to read but also want it to be as scientifically accurate as possible. Please include in the results section of your structured abstract (and, of course, in the article's results section) the following terms, as appropriate:

 For a clinical trial: 

• Absolute event rates among experimental and control groups
• RRR (relative risk reduction)
• NNT or NNH (number needed to treat or harm) and its 95% confidence interval (or, if the trial is of a public health intervention, number helped per 1000 or 100,000)

 For a cohort study: 

• Absolute event rates over time (eg 10 years) among exposed and non-exposed groups
• RRR (relative risk reduction)

 For a case control study: 

• OR (odds ratio) for strength of association between exposure and outcome

 For a study of a diagnostic test: 

• Sensitivity and specificity
• PPV and NPV (positive and negative predictive values)

The box stating what is known and what this paper adds (see below) should also reflect accurately the above information. Under what this paper adds please give the one most useful summary statistic eg NNT.

Please do not use the term "negative" to describe studies that have not found statistically significant differences, perhaps because they were too small. There will always be some uncertainty, and we hope you will be as explicit as possible in reporting what you have found in your study. Using wording such as "our results are compatible with a decrease of this much or an increase of this much" or “this study found no effect” is more accurate and helpful to readers than “there was no effect/no difference”.  Please use such wording throughout the article, including the structured abstract, and the box stating what the paper adds.

Structured abstract

Please ensure that the structured abstract is as complete, accurate, and clear as possible—but not unnecessarily long—and has been approved by all authors. We may screen original research articles by reading only the abstract. For randomised controlled trials please provide all the information required for a CONSORT style abstract. Please note the general rules for abstracts in the BMJ:

• should be 250- 300 words long: you may need up to 400 words, however, for a CONSORT abstract. (MEDLINE allows a maximum of 4096 characters but will truncate longer abstracts)
• use active voice but avoid “we did” or “we found”
• numbers over 10 do not need spelling out at the start of sentences
• sentences starting with a number do not require a capital letter
• p values should always be accompanied by supporting data and denominators should be given for percentages
• abstracts do not need references

The first few items (objective, design, setting) may be note-like and need not form full sentences. The results and conclusions sections should be written properly. Do not mix notes and full sentences in one section.

If the standard headings do not suit the type of study, substitute something sensible such as "population" as a heading instead of "participants" in an economics article. Please do not simply delete the heading.

For standard original research articles please provide the following headings and information (for RCTs please add the trial registration details - but there is no need to provide the additional subheadings which are used in the CONSORT statement on abstracts, as long as you include all the required information): 

• objectives - a clear statement of the main aim of the study and the major hypothesis tested or research question posed 
• design - including factors such as prospective, randomisation, blinding, placebo control, case control, crossover, criterion standards for diagnostic tests etc 
• setting - include the level of care eg primary, secondary; number of participating centres. Be general rather than give the name of the specific centre, but give the geographical location if this is important
• participants (instead of patients or subjects) - numbers entering and completing the study, sex, and ethnic group if appropriate. Give clear definitions of how selected, entry and exclusion criteria
• interventions - what, how, when and for how long. This heading can be deleted if there were no interventions but should normally be included for randomised controlled trials, cross over trials, and before and after studies. 
• main outcome measures - those planned in protocol, those finally measured (if different, explain why) 
• results - main results with (for quantitative studies) 95% confidence intervals and, where appropriate, the exact level of statistical significance and the number need to treat/harm. 
• conclusions – primary conclusions and their implications, suggesting areas for further research if appropriate. Do not go beyond the data in the article. Conclusions are important because this is often the only part that readers look at.
• trial registration - registry and number (only for clinical trials)

Please note that confidence intervals should be written in the format (15 to 27) within parentheses, using the word "to" rather than a hyphen.

Abstracts for meta-analyses and systematic reviews should have these headings:

• objective – what the review set out to determine
• design – type of meta-analysis, systematic review
• data sources - where included studies were retrieved from
• review methods - inclusion and exclusion criteria
• results - main findings with 95% confidence intervals
• conclusions -  primary conclusions and their implications

Abstracts for qualitative research articles should follow the standard style but may need fewer headings:

• objective      
• design
• participants
• setting
• results
• conclusions             

Quality improvement reports also have their own style of structured abstract:

• problem
• design
• setting
• key measures for improvement
• strategies for change
• effects of change
• lessons learnt

Structured discussion

Please ensure that the discussion section of your article follows this structure:

• statement of principal findings
• strengths and weaknesses of the study
• strengths and weaknesses in relation to other studies, discussing important differences in results
• meaning of the study: possible explanations and implications for clinicians and policymakers
• unanswered questions and future research

“What this paper adds” box

Please produce a box offering a thumbnail sketch of what your article adds to the literature, for readers who would like an overview without reading the whole article It should be divided into two short sections, each with 1-3 short sentences.

section 1:  What is already known on this subject
In two or three single sentence bullet points please summarise the state of scientific knowledge on this subject before you did your study and why this study needed to be done. Be clear and specific, not vague.

For example you might say: “Numerous observational studies have suggested that tea drinking may be effective in treating depression, but until now evidence from randomised controlled trials has been lacking/the only randomised controlled trial to date was underpowered/was carried out in an unusual population/did not use internationally accepted outcome measures/used too low a dose of tea.”

or: “Evidence from trials of tea therapy in depression have given conflicting results. Although Sjogren and Smith conducted a systematic review in 1995, a further 15 trials have been carried out since then…”

section 2:  What this study adds
In one or two single sentence bullet points give a simple answer to the question “What do we now know as a result of this study that we did not know before?” Be brief, succinct, specific, and accurate. For example: “Our study suggests that tea drinking has no overall benefit in depression”. 

You might use the last sentence to summarise any implications for practice, research, policy, or public health. For example, your study might have: asked and answered a new question (one whose relevance has only recently become clear) contradicted a belief, dogma, or previous evidence provided a new perspective on something that is already known in general provided evidence of higher methodological quality for a message which is already known.

Title page

This should give the title of the article, including the study design. Please give for each author his or her name and initials, full address including postal code and one main work position (job title) at the time of writing the paper. We do not need authors’ qualifications. For the corresponding author please provide an email address and the best contact address: this may differ from his or her work address.

Other items to include with your original research article

• a word count for the main text (excluding the abstract, references, tables, boxes, or figures): you will be asked to enter this when you upload your manuscript at submit.bmj.com
• original raw data if you think they will help our reviewers or if we specifically request them 
• copies of any non-standard questionnaires and assessment schedules used in the research 
• references to any non-standard statistical packages used to analyse the data. There is no need to cite a package as widely used as STATA, but please say if you have used a package that might be unfamiliar to general readers eg RevMan for a systematic review
• copies of patient information sheets used to obtain informed consent  for the study
• copies of related articles you have published. This is particularly important when details of the study methods are published elsewhere 
• copies of any previous reviewers' reports on this article. We appreciate that authors may have tried other journals before sending their work to the BMJ. Please let us know how you have responded to previous reviewers' comments before submission 
• names and contact details (including email addresses) of suitable peer reviewers; we often find authors' suggestions helpful
  

Please provide all of the above (if not done earlier) with your revised article as well as a detailed covering letter explaining how you have responded to editorial and peer review comments and other guidance from the BMJ. All of this should be submitted via our online editorial office.

Commentaries on research

We often publish original research articles with an accompanying commentary of up to 500 words and five references, commissioned to help readers interpret the research or place it in context. If we commission a commentary on your article we will send you a copy of it before publication. 

If we ask you to write a commentary, please provide in the manuscript a title for your piece; a title page giving your name, position, and contact details including email address; and statements of competing interests and – if appropriate -  contributorship and funding. Please say in your covering letter or email which BMJ article you are commenting on and give its BMJ manuscript number.