Sex in experimental design - MRC

The Medical Research Council (MRC) is committed to funding the best quality medical research, which is relevant to and benefits the whole of society.

Guidance on new requirements

MRC will soon require sex to be specified in the experimental design of grant applications involving animals, and human and animal tissues and cells.

This will include reporting the sex in experiments using cells and tissues. If you don’t know the sex of the cells and tissues you use, you should plan to determine it as part of your proposed research.

These expectations will start to apply later in 2022 and from 2023.

Use of both sexes will be the default

MRC will expect both sexes of animals, tissues and (non-immortalised) cells to be used as default in research proposals.

MRC will continue to fund research proposals based on the assessment of the quality of the research and value for money in terms of the resources requested.

This includes whether or not the funds requested are essential and adequate for the work, and justified by the importance and scientific potential of the research.

Justification for single-sex studies by exception

MRC may still fund single-sex studies where there is strong justification in the research proposal for doing so.

In cases of acutely scarce resources, purely molecular interactions or single sex mechanisms or diseases, the use of a single sex is likely to be appropriate.

Other reasons for conducting research in a single sex given by applicants will be considered as part of the peer review process but should have robust justification.

In most cases, female variability will not be sufficient as a justification for using only one sex. MRC will also not accept as justification that prior work has been performed in only one sex, or that there is a lack of evidence of sex having an effect.

Use the National Centre for the Replacement, Refinement and Reduction of Animals in Research’s Experimental Design Assistant to help you plan your experiments using both sexes.

Help us implement the new requirement

MRC is committed to helping the research community embed consideration of diversity into their research design.

MRC would like to get your views to understand how best to implement these changes, and what support researchers and research support teams might need in order to meet the new expectations.

Respond to our consultation on the UK Research and Innovation engagement hub by 24 April 2022.

How we developed this requirement

These changes are based on the recommendations of a recently convened working group of experts in biomedical research, statistics and experimental design.

Alongside advice from the expert working group, MRC carried out a survey of the research community in 2021.

The scope of the survey covered aspects of diversity (including sex) in health and biomedical research involving:

  • human participants
  • animal subjects
  • in vitro work.

It sought to understand current research practices, community perceptions, as well as benefits of and barriers to increasing diversity in research.

The survey showed that the majority of MRC researchers saw the benefits of considering diversity in their research. The most frequently cited benefits were increased translatability and reproducibility of research, as well as detecting sex specific results.

The most common barriers and concerns mentioned were the:

  • potential increase in the cost of experiments and complexity of research design
  • compliance with the principles of the 3Rs (the reduction, replacement and refinement of the use of animals)
  • commercial availability of samples.

Almost all respondents felt there was a need to develop guidance about sex in animal research, and there was a high level of support for funders taking on this role.

Contact us about the new requirement


Last updated: 14 March 2022

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