Women in medical research: the gender health gap in numbers

SASian Anderson, Writer and editor, MyGLP. Sources checked 5 November 2026.

What the government itself found

The 2022 Women's Health Strategy for England put the problem in plain words. It said a "male as default" approach had been seen in research and clinical trials, in the training of healthcare professionals, and in the design of health services. It also said women spend a significantly greater share of their lives in ill health and disability than men, and that women are under-represented in important clinical trials.

The call for evidence behind that strategy drew 97,307 responses from England. 84% said there had been times when women were not listened to by healthcare professionals. Respondents also asked for women of every background to be represented in clinical trials.

None of this is about women against men. Men are colleagues, researchers and partners in fixing it. The point is evidence: a treatment tested mostly in one kind of body is less well understood in another.

Why women were left out of trials

For decades, many trials excluded women who could become pregnant, out of concern about harm to a pregnancy. In the United States, the 1993 NIH Revitalization Act was the law that first required women to be enrolled in federally funded late-stage trials. A 2020 review in Biology of Sex Differences describes this history.

Side effects: the clearest evidence of the gap

The same review, by Zucker and Prendergast, looked at medicines with known differences in how men and women absorb and clear them. When a dose is set from trials run mostly in men, women can end up with more drug in the blood for longer.

The UK research funder NIHR gives its own examples in its sex and gender policy guidance. Antipsychotics are dosed the same way for both sexes, so women often receive more than they need and have more side effects. When beta blocker data were finally split by sex, women given the drug in one recent study were nearly three times more likely to die than women not given it.

Heart trials still short of women

Heart disease is where the gap costs most. A 2025 analysis of 1,593 cardiovascular trials published between 2018 and 2024 found women made up 38.5% of nearly 1.9 million participants. Researchers compare the share of women in a trial with the share of women who have the disease. A ratio between 0.8 and 1.2 counts as fair. The median was 0.77, and in trials of the heart artery disease behind most heart attacks it was 0.57. There was no significant improvement over the six years.

The consequences show up in care. The British Heart Foundation reports that women are less likely to get the right first diagnosis after a heart attack, and even when correctly diagnosed are about half as likely as men to receive recommended treatments. Our heart attack guide covers the symptoms and the numbers.

Three safety reviews that centred women

In July 2020 the Independent Medicines and Medical Devices Safety Review, chaired by Baroness Cumberlege, examined how the health system responds when patients raise safety concerns. Its three cases were vaginal mesh, the epilepsy drug sodium valproate taken in pregnancy, and the hormone pregnancy test Primodos. Each one affected women and their children. The review made nine recommendations.

Diagnosis delays

The research gap feeds diagnosis delays. At the launch of the renewed strategy, Endometriosis UK said the average time to an endometriosis diagnosis is 9 years and 4 months, rising to 11 years for women from diverse ethnic communities. The charity's 2023 survey across the UK put the average at 8 years and 10 months. The endometriosis guide explains what to ask for. Autoimmune conditions, which are far more common in women, follow a similar pattern, which our autoimmune guide covers.

What is changing in the UK

• From 27 November 2024, NIHR made inclusive research design a condition of funding for UK studies.
• From 10 November 2025, NIHR applicants must explain how sex and gender are accounted for, justify single-sex designs, plan analysis split by sex, and report on it during the study.
• The 2022 strategy committed to encourage all publicly funded health research to report the sex breakdown of participants, and set up a roundtable led by Professor Lucy Chappell on how to tackle the under-representation of women.
• NIHR, which spends £1 billion a year of health department money on research, now records the sex of study participants in its equality data. The Medical Research Council spent £96 million on women's health research from 2017 to 2021.
• The renewed Women's Health Strategy, published on 15 April 2026, sets a 10 year plan built on women having "voice, choice and power" in their care.

Weight loss medicines and women

For weight loss medicines, the open questions are specific to women: periods, contraception, pregnancy and the menopause. Our guides on contraception and perimenopause set out what the leaflets and trials say.

What this means for you

• If a side effect feels worse than expected, say so. Women's higher exposure to some drugs is documented, and a dose change is a reasonable request.
• Ask whether a treatment was tested in people like you: your sex, age and ethnicity.
• If you are invited into a trial, saying yes adds women to the evidence. The decision is yours.
• Use the GP preparation guide to bring your own evidence to appointments.

Sources

1. Women's Health Strategy for England (2022) (Department of Health and Social Care)
2. Results of the Women's Health: Let's talk about it survey (Department of Health and Social Care)
3. Sex differences in pharmacokinetics predict adverse drug reactions in women (Zucker and Prendergast, Biology of Sex Differences, 2020)
4. Sex and gender in research: guidance for applicants (National Institute for Health and Care Research)
5. Consideration of sex/gender aspects in cardiovascular clinical trials (Bley et al, Clinical Research in Cardiology, 2025)
6. Women and heart attacks (British Heart Foundation)
7. Independent Medicines and Medical Devices Safety Review report (Department of Health and Social Care)
8. Women's voices to be at the heart of renewed health strategy (Department of Health and Social Care)
9. Renewed Women's Health Strategy for England (2026) (Department of Health and Social Care)