Women in Clinical Trials: What the Data Show

Are women in clinical trials represented at rates that match their disease burden?

Women in clinical trials are not consistently represented at rates that match their share of disease burden — a pattern that a 2025 analysis of FDA-approved drugs found holds across multiple therapeutic areas. That gap matters directly for anyone trying to understand what trial data actually tells us about a medicine's effects in women.

A systematic review of FDA-approved drugs from 2015 to 2023 examined whether the sex breakdown of trial participants matched the sex breakdown of people living with each condition. The researchers found that women were underrepresented relative to disease burden in several indication categories, meaning the data used to approve those drugs came disproportionately from men — even when women carry a larger share of the disease. This is a structural evidence gap, not a gap in individual women's willingness to participate.

The problem compounds across conditions. Women make up the majority of people living with Alzheimer's disease, yet a call to action on atypical Alzheimer's variants identified that trial designs routinely exclude or undercount the populations — including older women — who bear the greatest burden of the disease. Separate cardiovascular research has documented that women face specific structural barriers to trial participation: scheduling conflicts tied to caregiving, distrust built from historical exclusion, and consent processes that do not account for their circumstances.

The evidence describes several concrete patterns:

• Women in hypertension and diabetes trials at Federally Qualified Health Centers were enrolled at rates that did not reflect their prevalence in those patient populations, according to a 2025 systematic review and meta-analysis.
• Cancer trial research found that "bright spot" sites — those that successfully enrolled underrepresented groups — used community-based outreach and flexible scheduling. The gap is addressable, not fixed.
• Trial leadership shapes trial design. A review of oral and maxillofacial surgery research found significant gender disparities in who leads trials, which can affect which questions get asked and which populations get prioritized in study design.

When a drug label reports efficacy or side-effect data, that data reflects whoever was enrolled. If women in a given study were underrepresented, the label's numbers may not describe women's experiences with the same precision they describe men's. Asking a clinician "how many women were in the trial that supports this medicine?" is a reasonable, answerable question — and the answer shapes how much confidence anyone can place in the reported outcomes.

This section is for general health education only and does not constitute medical advice. Consult a qualified healthcare provider before making any decisions about medicines or treatments.

Which disease areas show the largest sex representation gaps?

The largest sex representation gaps in women in clinical trials appear in cardiovascular disease, metabolic conditions like diabetes, and neurology — areas where the disease burden in women is high but trial enrollment has historically skewed male. A drug tested mostly in men may behave differently in women's bodies, and without that data, neither patients nor clinicians can know what to expect.

Cardiovascular disease

A 2025 cross-sectional analysis of FDA-approved drugs from 2015 to 2023 found that sex representation in trials frequently did not match the actual share of women living with the condition being studied. Cardiovascular indications showed some of the widest mismatches between disease burden and enrollment. Women in this study were underrepresented relative to how many women carry cardiovascular disease in the general population.

Patients in a qualitative cardiovascular research study named distrust, scheduling conflicts, and lack of culturally relevant outreach as specific barriers to trial participation. These barriers fall unevenly on women, particularly those with caregiving responsibilities.

Diabetes and hypertension

A systematic review and meta-analysis examining hypertension and diabetes trials at Federally Qualified Health Centers found that women and historically underserved populations were underrepresented across both disease areas. Women in this study made up a smaller share of trial participants than their share of the affected population would predict.

Neurology and Alzheimer's disease

Women develop Alzheimer's disease at higher rates than men, yet trial design has not consistently reflected that reality. A call-to-action paper on atypical Alzheimer's variants identified gaps in how trials recruit and characterize participants across disease subtypes — gaps that affect the quality of evidence available for any subgroup, including women. A systematic review of anxiety outcome measures in dementia trials (source) found that patient-reported tools were inconsistently applied, which limits what researchers can learn about symptom experience across sexes.

What the gaps mean practically

When a drug label reports data from a trial that enrolled 20–30% women, the prescribing information reflects that limited sample. The trial did not establish how the drug performs across the full range of female biology, including differences in body composition, hormonal variation across the lifespan, or age-related changes. Gaps in trial leadership compound enrollment gaps: a cross-sectional study in oral and maxillofacial surgery found that women were underrepresented among principal investigators, which shapes which research questions get asked in the first place.

The evidence base is uneven. Age, race, ethnicity, and life stage all interact with sex in ways that most trials have not yet captured, and the gaps are not uniform across all disease areas or all women.

This content is for general health education only and is not medical advice. Consult a qualified healthcare provider before making any decisions about your care.

Why do women and underserved groups enroll in trials at lower rates?

Women and underserved groups enroll in clinical trials at lower rates because structural barriers — not personal disinterest — keep them out. Research on enrollment patterns points to a cluster of practical, historical, and design-level problems that compound each other.

Practical barriers come first. A qualitative study of cardiovascular research found that patients named transportation, work schedules, and childcare as the most immediate reasons they declined or never considered joining a trial — patient perspectives in cardiovascular research. Trial sites cluster in academic medical centers far from the communities where many women, lower-income patients, and patients of color actually receive care.

Trust is a separate, serious problem. The same cardiovascular study found that historical mistreatment in medical research — including documented abuses against Black Americans — left lasting skepticism about whether researchers would protect participants' interests. That skepticism is rational, not irrational. Rebuilding it takes time and consistent community presence, not a single recruitment flyer.

Trial design itself screens people out. Eligibility criteria that exclude patients managing multiple health conditions, or that require frequent in-person visits, disproportionately affect women who are older, caregiving, or managing chronic illness. A systematic review of cancer trial enrollment identified overly restrictive eligibility criteria as one of the most modifiable barriers to inclusive participation — strategies for enhancing participation.

Federally Qualified Health Centers (FQHCs) — clinics that serve low-income and uninsured patients — rarely run trials at all. A systematic review and meta-analysis found that representation of women and historically underserved populations in hypertension and diabetes trials conducted at FQHCs was low, partly because those sites lack the infrastructure to host research — representation of women and underserved populations. Patients who receive care only at FQHCs are effectively invisible to most trial datasets.

Language and literacy add another layer. Consent forms written at a graduate reading level, available only in English, exclude people who speak other languages or who have lower health literacy — informed consent disclosures.

The result is a cycle: underrepresentation in trials produces drug labels with thin data on women and underserved groups, which makes clinicians less confident prescribing to those patients, which reduces demand for trials that include them. Breaking that cycle requires changes at the trial design stage — not at the patient level.

This section is for general health education only and is not medical advice. Speak with a qualified clinician about your own care.

What does poor trial representation mean for women's health decisions?

When women in clinical trials are underrepresented, the evidence base for a medicine reflects a narrower slice of human biology than the people who will actually use it. Sex-based differences in how the body absorbs, processes, and responds to a drug can be real and clinically meaningful.

A 2025 systematic review examining FDA-approved drugs from 2015 to 2023 found that sex representation in trials frequently did not match the actual disease burden in women. Women carried a significant share of the disease, but the trial populations studying those diseases skewed male. When a drug is approved on data that skews male, the label's safety and dosing information reflects that skew.

What does this mean in practice?

• A trial that enrolled mostly men cannot tell you how a peptide medicine behaves across the hormonal variation present in different life stages in people with female reproductive biology.
• The label reports what the trial established. If the trial did not establish how a drug performs in women across different age groups or hormonal contexts, the label cannot tell you either.
• A qualitative study on cardiovascular research found that patients from underrepresented groups named distrust and structural barriers as reasons they stayed out of trials—meaning the gap is not random, and it compounds over time.

Representation gaps vary by condition. The 2025 FDA drug review found that some therapeutic areas showed closer sex parity than others, so the degree of uncertainty is not uniform across all peptide medicines. Ask specifically about the trial population for the drug you are considering.

None of this means a medicine is unsafe for you. It means the evidence available to your clinician may be thinner for your sex, age group, or life stage than it is for others. A systematic review on hypertension and diabetes trials found that historically underserved populations—including women—were consistently underenrolled at Federally Qualified Health Centers, which are the primary care settings many people rely on most.

You can ask your clinician a direct question: what does the trial population for this medicine actually look like, and what does the label report about people with my biology?

This content is for general health education only and is not medical advice. Consult a qualified healthcare provider before making any decisions about medicines or treatments.

Are there proven strategies that increase enrollment of underrepresented patients?

Yes, proven strategies do increase enrollment of underrepresented patients — including women in clinical trials — and the evidence points to specific, repeatable practices rather than vague good intentions.

The clearest picture comes from a qualitative study of cardiovascular research participants, which found that trust-building between research teams and communities was the single most cited factor shaping whether patients agreed to join a trial. Patient Perspectives in Cardiovascular Research identified concrete trust-builders: community health workers who shared patients' backgrounds, study staff who explained procedures in plain language, and researchers who returned results to participants rather than disappearing after data collection ended.

Cancer trial research adds structural detail. A systematic review of "bright spot" cancer programs — sites that consistently enrolled more diverse patients than peer institutions — found several shared practices: embedding trial coordinators inside community clinics rather than academic medical centers, offering transportation reimbursement and flexible scheduling, translating consent forms into patients' primary languages before recruitment began rather than after, and training staff to recognize and address implicit bias in referral patterns. Strategies for enhancing participation reported that sites using three or more of these approaches simultaneously showed the largest enrollment gains among Black, Hispanic, and low-income patients.

Federally Qualified Health Centers (FQHCs) — clinics that serve patients regardless of ability to pay — represent a specific opportunity. A systematic review and meta-analysis of hypertension and diabetes trials at FQHCs found that women and historically underserved populations were enrolled at higher rates at these sites than at traditional academic centers, though the review also noted that reporting on race, ethnicity, and sex remained inconsistent across included studies. Representation at FQHCs concluded that partnering with FQHCs is a documented pathway to broader enrollment, not a theoretical one.

One gap the evidence does not yet close: most strategy research measures enrollment numbers, not whether enrolled participants stay through trial completion or whether data from diverse groups is analyzed and reported separately. Joining a trial matters less if your subgroup's results are pooled away into an aggregate that obscures differences by sex, age, or life stage.

This section is for general health education only and is not medical advice. Speak with a qualified clinician about your own care.