About 3.5% of the U.S. population is misdiagnosed every year, according to a new study from The Schiller Kessler Group, the Florida personal injury firm behind InjuredInFlorida.com. That rate translates to roughly 12 million American adults annually, based on Johns Hopkins Medicine data. The consequences are severe: an estimated 795,000 Americans are seriously harmed by diagnostic errors each year, including 424,000 who are left permanently disabled and 371,000 who die. The study, “America’s Most Commonly Misdiagnosed Conditions,” examines which illnesses are most often missed, what they are mistaken for, and which patients are most likely to be dismissed.
The highest misdiagnosis rates are found among chronic and autoimmune conditions that develop slowly and share symptoms with more common illnesses. Endometriosis, which affects about 1 in 10 women of reproductive age, is misdiagnosed in 75% of cases and is frequently mistaken for irritable bowel syndrome, ovarian cysts, or appendicitis. Patients wait an average of 11 years for a correct diagnosis, and Black women are 50% less likely than White women to be correctly diagnosed. Fibromyalgia, which affects about 10 million Americans, carries a 50% misdiagnosis rate, while lupus, affecting roughly 1.5 million Americans, is misdiagnosed 46.5% of the time and takes about six years on average to identify. Black women develop lupus at roughly three times the rate of White women, with onset about six years earlier. Lyme disease, diagnosed about 475,000 times a year, is misdiagnosed in 30% to 50% of cases, often as multiple sclerosis, fibromyalgia, or lupus, and celiac disease, affecting about 1 in 133 Americans, is missed in about 25% of cases, usually mistaken for IBS.
Mental health and neurological conditions show similar patterns. Bipolar disorder, which affects about 5.7 million U.S. adults, has a 69% misdiagnosis rate and is most often mistaken for major depression, with more than a third of patients waiting over 10 years for an accurate diagnosis. That error carries a specific danger, as antidepressants prescribed for depression can trigger mania in patients who actually have bipolar disorder. Multiple sclerosis, affecting about 1 million Americans and women at nearly three times the rate of men, is misdiagnosed in about 18% of cases, often as migraine. At the time of diagnosis, 38.3% of Black MS patients had already experienced vision loss compared with 28.6% of White patients.
Acute, time sensitive emergencies are also missed at alarming rates. Stroke strikes about 795,000 Americans every year, roughly one every 40 seconds, and is misdiagnosed in about 17% of cases, commonly as migraine, vertigo, or an inner ear infection. A 2024 analysis of more than 34,500 cases found strokes were missed more often in Black patients (34.9%) than in White patients (31.4%). Heart attacks, which occur about 805,000 times a year, are frequently mistaken for anxiety or panic attacks, and women face up to a 59% higher chance of misdiagnosis than men. Lung cancer, with 226,650 projected U.S. diagnoses in 2026, is misdiagnosed as pneumonia or bronchitis in 25% of cases, a delay that matters enormously: five year survival is about 60% to 65% when caught early but just 12% at stage four.
The study highlights that misdiagnosis risk is not evenly distributed. A 2024 Johns Hopkins analysis found that women and racial or ethnic minorities are up to 30% more likely than White men to be misdiagnosed. ECRI ranked “medical gaslighting” as the number one concern in its 2025 Top 10 Patient Safety Concerns report, and a HealthCentral reader survey found that 94% of respondents said a doctor had ignored or dismissed their concerns, 55% said their condition worsened as a result, and 28% experienced a resulting health emergency.
Misdiagnosis also fuels a second wave of harm through incorrect treatment. According to the Agency for Healthcare Research and Quality, adverse drug reactions cause about 700,000 emergency room visits and 100,000 hospital admissions each year, and a 2025 American Society of Pharmacovigilance study estimated drug related harm may kill up to 300,000 Americans annually. Nearly a third of outpatient antibiotic prescriptions are written for infections that are not bacterial, and more than 94% of adverse drug reactions go unreported.
The financial toll is staggering. Diagnostic errors account for an estimated 17.5% of U.S. healthcare spending, about $870 billion a year. For individual patients, a repeat MRI after a misdiagnosis can cost up to $2,000 at an independent center or $8,000 at a hospital, on top of an average health insurance deductible of $1,886.
The study identifies “premature closure,” the tendency to settle on the first plausible explanation and stop investigating, as the cause of about 47% of diagnostic errors. Its central message is that clinicians should continue asking questions and ordering tests until a diagnosis is confirmed, and that patients should feel empowered to push for answers when symptoms persist.
