Women suffer from side effects of medication nearly twice as often as men. The reason is not that women are more sensitive. The reason is that most medications were developed using male biology, dosed for male bodies, and prescribed to women without the necessary data. Here you will learn how this came about and why it still matters today.
For over two decades, millions of women in the US and Europe took the wrong dose of Ambien every night.
The US Food and Drug Administration (FDA) approved zolpidem, the active ingredient in Ambien, in 1992. It was tested primarily on men. It was dosed for men. And it was prescribed to women in the same dose, without anyone ever investigating how the female body metabolizes it. Because that research never took place.
Women break down zolpidem 50% more slowly than men. The same dose that was largely eliminated in men by morning was still circulating in women's blood at dangerous concentrations when they got behind the wheel.
It took twenty-one years and an archive of court records involving women charged with drunk driving and violent crimes who had no memory of the acts—all while on a correctly prescribed sleep aid at a dose their bodies could not break down—before the FDA halved the recommended dose for women in 2013.
After the change, reported side effects in women dropped by 38%. These 38% represent twenty-one years of preventable harm.
Ambien is not an isolated case. It is just the example that became too public to ignore. The same gap exists with antidepressants, cardiovascular drugs, antipsychotics, painkillers, anticoagulants, and dozens of other drug classes that women take daily in a dosage designed for a different body.
Why the female body processes medication differently
The differences in drug metabolism between men and women are not subtle.
Women generally have lower activity in key liver enzymes, especially CYP3A4. This enzyme breaks down a significant portion of medications approved today. Lower enzyme activity means: drugs are broken down more slowly, remain in the body longer, and reach higher peak concentrations than the same dose in a man.
In addition: women have a higher percentage of body fat, different renal excretion, a different gastric emptying rate, and hormonal fluctuations throughout the cycle, which can change drug metabolism by up to 30% depending on the cycle phase.
The birth control pill can reduce the effectiveness of epilepsy medications by 50 to 60%. Women would therefore need to adjust their dose throughout their cycle, without ever being told that this interaction exists.
These are not fringe cases or rare sensitivities. They are documented physical realities of the female body that the pharmaceutical industry systematically ignored when medications were developed primarily on male test subjects.
A study in Biology of Sex Differences found a sex-based dosage gap in at least 86 FDA-approved drugs. These include aspirin, morphine, heparin, and antidepressants like sertraline and bupropion. Women broke down nearly all of these more slowly than men. In 96% of cases, this led to significantly higher side effect rates in women.
The medications were the same. The body was different. Research has never accounted for this difference.
The scale of the side effect problem
According to FDA data, women experience side effects 80 to 90% more frequently than men. Some analyses suggest nearly double the rate.
In the US, women account for about 59% of all filled prescriptions. They are therefore the primary users of the pharmaceutical system and are harmed by it significantly more often than the group it was developed around.
This is not a rare exception. It is the normal experience of being a female patient taking medication that was developed, tested, and dosed for someone else.
Digoxin, a heart medication prescribed to millions, produces 20 to 30% higher blood concentrations in women at the standard dose. This increases the risk of toxicity by 40% and leads to nausea, confusion, and dangerous cardiac arrhythmias.
SSRI-type antidepressants trigger nausea and dizziness 1.5 to 2 times more often in women than in men. Antipsychotics like haloperidol carry a 2.3-fold higher risk of dangerous cardiac arrhythmias in women.
These are not theoretical risks from small studies. They are documented, published, and in most cases known for years before the dosage was adjusted. Assuming it was adjusted at all.
It is not just about Ambien—that is only the tip of the iceberg. Sex-based differences exist for many medications. Some are well known, others are barely noticed.
— Dr. Janine Clayton
How exclusion from research created the dosage problem
The dosage problem is the direct result of exclusion from research.
In 1977, the FDA recommended excluding women of childbearing age from early phases of drug trials. The intention was to protect unborn children from experimental substances following the thalidomide scandal.
The result was that for sixteen years, the pharmacokinetic data that determines dosage—how quickly a drug is absorbed, how it is distributed in the body, how it is metabolized, and how it is excreted—was collected almost exclusively from male subjects.
By the time women were finally included in studies after the 1993 NIH Revitalization Act, the dosages had long been set. And the tacit assumption that male data could be transferred to female bodies was already inscribed into clinical guidelines, prescribing habits, and package inserts, which in many cases were never reviewed.
Even where women have been included in studies since 1993, sex-disaggregated analysis is not consistently required. That is, the practice of analyzing the results of male and female participants separately to identify differences.
Including women in a study is simply not the same as investigating how women respond. A study can have 40% female participants and still only report overall results that mask sex-specific differences in efficacy, side effects, and optimal dosage.
This gap between inclusion and analysis means that even the approval process after 1993 has yielded incomplete data on female physiology for many approved drugs.
When Dr. Mary Claire Haver, Dr. Vonda Wright, Dr. Stacy Sims, and Dr. Natalie Crawford appeared on The Diary of a CEO in October 2025, they spoke directly about the practical consequences of this research failure in everyday clinical practice.
Crawford described patients who were prescribed medication at standard doses and experienced side effects that were dismissed as anxiety, hypochondria, or personal sensitivity, rather than as a pharmacological reaction of a body for which the drug was never developed.
Wright described how the clinical guidelines she was trained under are based on research that systematically underrepresented the very patients she actually treats.
Sims, whose work focuses specifically on how female and male physiology differ in their response to nutrition, training, and active ingredients, has been documenting the practical consequences for years of the assumption that male data can be transferred directly to women. They cannot. The difference between male and female physiology is real, measurable, and consequential.
What this means beyond prescription drugs
The same logic applies to dietary supplements. The industry is less regulated than the pharmaceutical industry. Therefore, the requirement to include women in tests and analyze results by sex is applied even less consistently here.
Most formulas were developed from research on male subjects, often male athletes, and dosed based on male pharmacokinetics.
The female hormonal cycle changes how the body absorbs, distributes, metabolizes, and responds to active ingredients throughout the month. A formula created without woman-specific research cannot account for this.
The problem is not limited to prescription drugs under medical supervision. It affects every protein, every vitamin, every performance supplement, and every longevity compound that women buy in the assumption that it was developed with their biology in mind. In most cases, it was not.
Developing a product specifically for women requires female subjects in research, endpoints relevant to women in study design, and the intellectual honesty to state what is known and what is not.
The NMN study by Yoshino et al. (2021), the most-cited human study on NMN, was conducted exclusively with postmenopausal women and measured outcomes directly relevant to female metabolic health. This is not the norm. It is what it means to take biology seriously. And the fact that it stands out at all tells us more about the low baseline.
The supplement you take today was almost certainly developed without a woman in the room. The question is whether the brand you choose has changed anything about that.
Where science stands today
The 2024 FDA guideline has tightened requirements for diversity in clinical trials and emphasized the need for equitable representation in drug research. The US National Institutes of Health (NIH) now requires biological sex to be considered as a variable in preclinical research. This means animal studies must include female animals and report results by sex before human trials begin.
These changes are significant, and they are overdue. But they do not retroactively fix the decades of approvals based on male-only data. They do not change clinical guidelines that still do not reflect sex-specific dosages. And they do not change the prescribing habits of a medical profession trained on research that treated male biology as the universal standard.
A 2024 report by McKinsey and the World Economic Forum identifies insufficient science as one of three structural causes of the health gap. It notes that only about 10% of clinical trials for ischemic heart disease and migraine report sex-disaggregated data, even though both conditions disproportionately affect women or follow a different course in them.
The gap between what is known and what is applied in practice remains substantial in almost every medical field. And the women living in this gap are not abstract political problems. They are women taking medication in the wrong dosage, suffering preventable side effects, and being told their reaction is personal sensitivity rather than a pharmacological failure.
Ambien was the example that became too public to ignore. For dozens of other drugs, the evidence is just as clear and just as old. The research exclusion that created this problem is documented history. The dosage gap that resulted from it is current reality. And the assumption that male data could be transferred to female biology—scientifically unjustified and practically always harmful—is still embedded today in the systems that determine which medications women take and how much of them.
Sources
- Zucker, I., & Prendergast, B. J. (2020). Sex differences in pharmacokinetics predict adverse drug reactions in women. Biology of Sex Differences, 11(1), 32. https://doi.org/10.1186/s13293-020-00308-5
- US Food and Drug Administration. (2013). FDA drug safety communication: Risk of next-morning impairment after use of insomnia drugs containing zolpidem. https://www.fda.gov/drugs/drugsafety/ucm334033.htm
- Association of American Medical Colleges. (2024). Why we know so little about women's health. https://www.aamc.org/news/why-we-know-so-little-about-womens-health
- NIH Office of Research on Women's Health. History of women's participation in clinical research. https://orwh.od.nih.gov/toolkit/recruitment/history
- McKinsey Health Institute & World Economic Forum. (2024). Closing the women's health gap: A $1 trillion opportunity. https://www.mckinsey.com/mhi/our-insights/closing-the-womens-health-gap-a-1-trillion-dollar-opportunity-to-improve-lives-and-economies
- Haver, M. C., Wright, V., Sims, S., & Crawford, N. (2025, October 16). Hormone & fertility experts: We've been lied to about women's health. The Diary of a CEO with Steven Bartlett.
- Yoshino, M., Yoshino, J., Kayser, B. D., et al. (2021). Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science, 372(6547), 1224–1229. https://doi.org/10.1126/science.abe9985
- Frontiers in Pharmacology. (2023). A systematic review on sex differences in adverse drug reactions related to psychotropic, cardiovascular, and analgesic medications. https://doi.org/10.3389/fphar.2023.1096366