The women's health research gap: what the evidence shows

For most of modern medicine, the standard research subject was a man. Drug trials, lab animals, textbooks and even who got to become a doctor all leaned male. That history still shapes how medicines are tested, how research money is spent and how women are cared for today.

This article pulls together the best-sourced numbers we could verify, from government reviews, peer-reviewed studies and consultancy analyses. Each one is linked at the bottom. Where a number is narrower than it sounds, we say so.

The numbers at a glance

• 1977 to 1993: an FDA guideline recommended leaving women of childbearing potential out of early-phase drug trials, and stayed in place for 16 years.
• 8 of 10: prescription drugs withdrawn from the US market between 1997 and 2000 posed greater health risks for women than for men (GAO, 2001).
• 76 of 86: drugs with published sex-difference data had higher blood exposure in women (2020 review).
• $1.24 billion vs $44 million: raised by start-ups working on erectile dysfunction and other men's health concerns versus start-ups working on endometriosis, 2019 to 2023 (McKinsey, via the World Economic Forum).
• Under 1%: share of research funding received by six women-specific conditions that make up 14% of the women's health burden, 2019 to 2023 (World Economic Forum and McKinsey).

How women were left out of early drug research

In 1977 the FDA issued guidance recommending that women of childbearing potential be left out of early-phase (Phase 1 and early Phase 2) drug trials. One review of the period describes the result in plain terms: in practice, this resulted in the exclusion of women.

The FDA reversed this in 1993. The same year, Congress passed the NIH Revitalization Act (Public Law 103-43), which requires NIH-funded clinical research to include women unless there is a justified exception. NIH had encouraged inclusion since 1986, but the 1993 law made it a requirement.

The gap went beyond people. A 2011 review of 10 biological fields found male bias in 8 of them. In neuroscience, studies using only male animals outnumbered female-only studies 5.5 to 1.

The NIH did not expect researchers to account for sex as a biological variable in funded vertebrate animal and human studies until its policy took effect on January 25, 2016. The policy expects sex to be factored into design, analysis and reporting. It does not flatly require female animals in every study.

Who got to be a doctor

The research gap has a workforce history. Jefferson Medical College in Philadelphia, founded in 1824, did not admit women until 1961, and its first women graduated in 1965. That is 137 years without a female student.

A 2024 historical study found women made up about 6% of US doctors in 1910, and the share stayed between 4.5% and 6.5% until the 1960s. Women were 9.3% of medical college matriculants in 1965 and 28.7% by 1980, a period that included the civil rights era and Title IX in 1972.

The pattern was not only American. In 2018, a university-commissioned investigation found that Tokyo Medical University had been lowering women's entrance exam scores since 2006. A December 2018 review of 81 medical schools by Japan's education ministry found nine, including Tokyo Medical, Juntendo and Kitasato, had improper admissions practices based on factors that included sex and age.

What it means for the medicines women take

If early trials mostly enrolled men, doses can end up tuned to men. A 2020 review looked at 86 drugs with published sex-difference data. Women had higher blood exposure to 76 of them.

For the 59 drugs with clear side-effect data, higher exposure in women predicted more side effects in women in 88% of cases. The authors note that body weight alone did not explain the difference, and they recommend evidence-based dose reductions for women. These findings show a pattern. They are not proof that any single dose is wrong.

The best-known example is the sleep medicine zolpidem. Exposure ran 40 to 50% higher in women at the same dose, and weight explained only part of it. In 2013 the FDA lowered the recommended dose for women after reports of next-morning impairment.

A 2001 review by the US General Accounting Office found that 8 of the 10 prescription drugs withdrawn from the US market between January 1997 and December 2000 posed greater health risks for women than for men. For four of the eight, higher use among women may explain part of the gap. The other four caused more adverse events in women even though they were widely prescribed to both women and men.

An FDA clinical pharmacology review of 300 new drug applications from 1994 to 2000 found 11 drugs with a difference of more than 40% between men and women in how much of the drug reached the blood. None came with sex-specific dosing advice. That analysis is more than 20 years old, so read it as history. Today, sex-specific dosing instructions are still rare on US drug labels.

Where research money goes

A McKinsey analysis cited by the World Economic Forum found that 11 start-ups working on erectile dysfunction and other men's health concerns raised $1.24 billion from 2019 to 2023. Eight start-ups working on endometriosis raised $44 million. That counts start-ups, not conditions, and it covers private investment, not public research money.

A 2025 World Economic Forum and McKinsey analysis of research funding found that six women-specific conditions make up 14% of the total women's health burden but received under 1% of cumulative research funding from 2019 to 2023. The conditions are premenstrual syndrome, menopause, maternal haemorrhage, maternal hypertensive disorders, cervical cancer and endometriosis. By comparison, diabetes makes up 2% of the burden and received 12.5% of the funding in that analysis.

One analysis of NIH funding relative to disease burden found that for nearly three-quarters (25 of 34) of the diseases that mainly affect one sex, funding favored men. Women's diseases got less than their burden would predict, or men's diseases got more. Endometriosis, chronic fatigue syndrome and migraine were among the most underfunded relative to burden. It is a single-author study of 2015 to 2019 budget data, so read it as one analysis, not a final answer.

What happens in the clinic

A national study of emergency department visits for chest pain in adults 18 to 55 found women were less likely than men to be triaged as emergent (19.1% vs 23.3%) and to get an ECG (74.2% vs 78.8%). Women also waited longer to see a physician, independent of their clinical features.

In a study of heart attack patients, door-to-balloon time averaged 114.6 minutes for young women and 97.8 minutes for young men. The gap was not significant in older patients.

A 2023 meta-analysis of 24 studies of transcatheter aortic valve replacement, covering 92,499 patients, found women had about 1.8 times the risk of vascular complications compared with men. Researchers tie that to smaller blood vessels and large delivery sheaths. Newer, lower-profile devices have narrowed some gaps.

What doctors are taught

In a 2022 national survey of OB-GYN residency program directors, only 31% said their program has a menopause curriculum. In a 2017 survey of residents in family medicine, internal medicine and OB-GYN, about 1 in 5 (20%) said they got no menopause lectures during residency. Only 7% felt adequately prepared to manage menopause. That survey had 183 residents and a 26% response rate.

In one analysis of a widely used USMLE Step 1 review book, only 7.9% of the pharmacology content was sex- and gender-aware. That is a study prep book, not the exam itself.

In a 2025 survey at one US medical school, 71% of faculty respondents said considering sex and gender matters for patient care, but only 24% reported any formal or continuing education on it. There were 38 respondents, so this is a small snapshot.

Where the picture is more mixed

The story is not one-directional. A 2021 analysis of US clinical trials between 2000 and 2020 found women under-enrolled relative to disease burden in several fields, such as oncology (46% of the burden, 43% of participants) and neurology (56% and 53%). Those gaps are small, and male participants were under-represented in 8 other disease categories.

A 2026 study in Nature Communications found that therapies for female-predominant indications received 1.5 times more FDA approvals than male-predominant indications, and that female participation matched or exceeded disease prevalence in 67% of cases. Cardiovascular and autoimmune conditions were the most under-enrolled. Progress is real, and it is uneven.

What these numbers do not tell us

• Several figures come from consultancy analyses of public databases. They are checkable, but they are not peer-reviewed studies.
• Most findings show associations. They do not prove that missing women from research caused any single outcome.
• Individual studies are small, dated or limited to one school, one clinic or one drug.
• Nothing here is medical advice. If you take a medicine and have questions about your dose, talk with a clinician or pharmacist before changing anything.

Frequently asked questions

Were women banned from clinical trials?

Not by law. A 1977 FDA guideline recommended leaving women of childbearing potential out of early-phase trials, and in practice that often meant exclusion. The FDA reversed the guidance in 1993, and Congress passed the NIH Revitalization Act the same year.

Do women need different drug doses?

For some drugs, the evidence suggests yes. Zolpidem is the best-known case: the FDA lowered the recommended dose for women in 2013. For most drugs, sex-specific dosing instructions are absent from the label, so ask a pharmacist or clinician if you have concerns.

Is there still a gap in women's health research funding?

Analyses point to one. A World Economic Forum and McKinsey review found six women-specific conditions that make up 14% of the women's health burden received under 1% of cumulative research funding from 2019 to 2023. A separate analysis of NIH data found funding favored men in nearly three-quarters of the diseases that skew toward one sex.

How many women are in clinical trials today?

It depends on the field. A 2021 analysis found women under-enrolled relative to disease burden in oncology, neurology, immunology and nephrology, while a 2026 study found female participation matched or exceeded disease prevalence in 67% of cases.

Related reading

• Why women's health is decades behind: the research gap
• Dosed like a smaller man: why women get the wrong drug doses
• Why medicine is not one-size-fits-all for men and women
• Why women were left out of clinical trials, and what changed
• Do women need different drug doses? What the research says
• Women's health research funding: the gap in numbers
• Gender gaps in care: from the emergency room to heart procedures
• How women entered medicine, and what doctors are still taught

Sources

1. AAMC, Why we know so little about women's health (2024).
2. NIH Revitalization Act of 1993, Public Law 103-43, Section 131. FDA, Study and Evaluation of Gender Differences in the Clinical Evaluation of Drugs (1993). FDA, General Considerations for the Clinical Evaluation of Drugs (1977).
3. Beery AK, Zucker I. Sex bias in neuroscience and biomedical research. Neuroscience and Biobehavioral Reviews, 2011 (PMID 20620164).
4. NIH policy on sex as a biological variable, notice NOT-OD-15-102, effective January 25, 2016. See NIH Office of Research on Women's Health authors, 2022.
5. Zucker I, Prendergast BJ. Sex differences in pharmacokinetics predict adverse drug reactions in women. Biology of Sex Differences, 2020. Includes the FDA review of 300 new drug applications (Fadiran et al.) and the zolpidem findings.
6. US General Accounting Office, Drug Safety: Most Drugs Withdrawn in Recent Years Had Greater Health Risks for Women, GAO-01-286R, January 2001.
7. World Economic Forum with McKinsey Health Institute, Closing the Women's Health Gap: A $1 Trillion Opportunity (2024), page 23.
8. World Economic Forum with McKinsey Health Institute, Blueprint to Close the Women's Health Gap (2025), section 2.2.1.
9. Mirin AA. Gender disparity in the funding of diseases by the US National Institutes of Health. Journal of Women's Health, 2021 (PMID 33232627).
10. Steinberg JR et al. Analysis of female enrollment and participant sex by burden of disease in US clinical trials between 2000 and 2020. JAMA Network Open, 2021.
11. Sex representation in trials relative to indication-specific disease burden in FDA-approved drugs, 2015 to 2023. Nature Communications, 2026.
12. Banco D et al. Sex and race differences in the evaluation and treatment of young adults presenting to the emergency department with chest pain. Journal of the American Heart Association, 2022.
13. Sex differences in symptom complexity and door-to-balloon time (VIRGO and SILVER-AMI). American Journal of Cardiology, 2023.
14. Influence of gender on transcatheter aortic valve implantation, meta-analysis. Reviews in Cardiovascular Medicine, 2023.
15. Allen JT et al. Survey of OB-GYN residency program directors on menopause training. Menopause, 2023 (PMID 37738034). Kling JM et al. Survey of residents in family medicine, internal medicine and OB-GYN on menopause training. Mayo Clinic Proceedings, 2019 (PMID 30711122).
16. Quantitative and qualitative analysis on sex and gender in preparatory material for national medical examination in Germany and the United States. Journal of Medical Education and Curricular Development, 2020.
17. Medical school faculty knowledge and attitudes toward sex and gender-based medicine. PRiMER, 2025.
18. Evens E. PlayDoc M.D. Social History of Medicine, 2024. Jefferson: Jefferson Digital Commons.
19. BBC News, BBC News report on Japan's education ministry review of medical school admissions, December 14, 2018.

This article is for general education and is not medical advice. Sources were checked in October 2026. Several figures come from secondary analyses, as noted above.