Emergency Room Misdiagnosis: 7.4 Million Diagnostic Errors in US ERs Every Year

Imagine walking into an emergency room in excruciating pain, trusting that the medical professionals there will figure out what’s wrong. Now imagine being sent home with the wrong diagnosis — only to discover days or weeks later that a critical condition was missed. For millions of patients each year, this is not a hypothetical scenario. It is a documented reality.

Emergency room misdiagnosis is one of the most pervasive and consequential problems in modern healthcare. A comprehensive report from the U.S. Department of Health and Human Services’ Agency for Healthcare Research and Quality (AHRQ), published in December 2022, found that approximately 7.4 million diagnostic errors occur in American emergency departments every year. That translates to about 1,400 misdiagnoses per emergency room annually — and the consequences range from unnecessary treatments and delayed care to permanent disability and death.

This article examines the full scope of emergency room diagnostic errors: the conditions most commonly missed, why these errors happen, who is most at risk, and — most importantly — what you can do to protect yourself and your loved ones.

What Is Emergency Room Misdiagnosis? A Definition

Emergency room misdiagnosis occurs when a patient visiting an emergency department receives an incorrect, incomplete, or delayed diagnosis that leads to inappropriate treatment or a failure to treat the actual condition. This includes three distinct categories of diagnostic error: a wrong diagnosis (being told you have condition A when you actually have condition B), a missed diagnosis (being sent home with no diagnosis when a serious condition exists), and a delayed diagnosis (receiving the correct diagnosis only after a clinically significant delay that allows the condition to worsen).

According to the National Academy of Medicine (formerly the Institute of Medicine), diagnostic errors are the most common, most costly, and most dangerous type of medical error. Unlike medication errors or surgical mistakes, diagnostic errors often go undetected because the patient may not return to the same facility — or may not survive long enough for the error to be identified.

The emergency department is a particularly high-risk environment for these errors. Physicians must make rapid decisions with incomplete information, often under extreme time pressure and while managing multiple critically ill patients simultaneously. These conditions create a perfect storm for diagnostic mistakes. If you’ve ever wondered whether your ER visit resulted in the right diagnosis, understanding the warning signs of a potential misdiagnosis is a critical first step.

The Alarming Scale of ER Diagnostic Errors: What the Data Shows

The scope of emergency room misdiagnosis is far larger than most patients — and many healthcare professionals — realize. The numbers tell a sobering story.

The landmark AHRQ systematic review, which analyzed nearly 300 studies published between January 2000 and September 2021, established the most comprehensive picture of ER diagnostic errors to date. The key findings include:

• 7.4 million patients are misdiagnosed in U.S. emergency departments annually
• The diagnostic error rate is approximately 5.7% — or 1 in every 18 ER visits
• Out of approximately 130 million annual ER visits in the United States, about 2% of patients experience an adverse event due to misdiagnosis
• 2.6 million patients per year experience preventable harm from ER diagnostic errors
• Approximately 370,000 patients are permanently disabled or die as a result
• About 90% of serious harms from ER misdiagnosis involve failures in the clinical assessment and reasoning process

To put these figures in perspective, 370,000 patients suffering permanent disability or death from ER diagnostic errors each year exceeds the annual death toll from many widely feared diseases. This is not a niche problem — it is a systemic crisis that affects emergency departments of every size and type across the country.

The researchers also found that these error rates are comparable to those in primary care and hospital inpatient settings, suggesting that diagnostic errors represent a healthcare-wide challenge rather than a failing unique to emergency medicine. Understanding the real cost of medical misdiagnosis in America — in lives, dollars, and human suffering — reveals just how deeply this problem runs.

How the U.S. Compares Internationally

Emergency department diagnostic errors are not limited to the United States. In the United Kingdom, a study published in BMJ Open that analyzed data from the National Reporting and Learning System (NRLS) found that diagnostic errors were a significant contributor to patient safety incidents in NHS emergency departments, with cognitive errors — such as premature closure and anchoring bias — being the most common factors. The NHS itself has acknowledged that overcrowding and staffing shortages in A&E departments contribute to increased diagnostic error rates.

In Australia, research from emergency departments has similarly identified diagnostic errors as a prevalent concern, particularly in pediatric emergency care. A prospective multicenter study published in Frontiers in Pediatrics found that diagnostic errors were common in acute pediatric respiratory disease presentations, underscoring that no healthcare system is immune to this challenge.

The 5 Most Commonly Misdiagnosed Conditions in the ER

Not all misdiagnoses carry equal risk. The AHRQ report identified five conditions that, when misdiagnosed in the emergency department, account for 39% of all serious misdiagnosis-related harms. These are the “Big Five” — the conditions that emergency physicians miss most often with the most devastating consequences.

1. Stroke

Stroke is the single most dangerous condition to miss in an emergency room. The AHRQ analysis found that stroke is misdiagnosed approximately 17% of the time in emergency departments. Even more alarming, when patients present with dizziness and vertigo — rather than classic stroke symptoms like facial drooping or arm weakness — the initial stroke diagnosis is missed up to 40% of the time. Atypical symptoms raise the odds of a missed stroke diagnosis approximately 14-fold compared with classic motor symptoms.

Stroke requires treatment within hours to prevent permanent brain damage or death, making every minute of delayed diagnosis potentially catastrophic. Young adults are particularly vulnerable to stroke misdiagnosis because physicians may not expect a stroke in someone under 45. Learn more about why stroke misdiagnosis in young adults happens and what to watch for.

2. Heart Attack (Myocardial Infarction)

Heart attacks are the second most commonly missed critical diagnosis in the ER. According to Johns Hopkins Medicine, once blood flow to the heart muscle is blocked, irreversible damage begins within approximately 30 minutes. Misdiagnosis delays lifesaving treatments such as percutaneous coronary intervention (PCI) and thrombolytic therapy.

Women are at particular risk of having a heart attack misdiagnosed. While men typically present with the “Hollywood heart attack” — crushing chest pain radiating down the left arm — women more often experience nausea, jaw pain, back pain, extreme fatigue, and shortness of breath. These symptoms are frequently attributed to anxiety, acid reflux, or musculoskeletal pain. If you or a loved one has heart concerns, understanding why getting a second opinion for heart disease could be lifesaving.

3. Aortic Aneurysm and Dissection

An aortic aneurysm is a potentially fatal bulge in the wall of the body’s largest artery. When the aortic wall tears (dissection), it creates a medical emergency with a mortality rate that increases by approximately 1–2% per hour without treatment. These conditions are frequently misdiagnosed as musculoskeletal back pain, kidney stones, or gastrointestinal issues because the pain can be diffuse and variable.

4. Spinal Cord Compression and Injury

Spinal cord compression — caused by conditions such as tumors, infections, or herniated discs — can lead to permanent paralysis if not diagnosed and treated promptly. In the emergency room, spinal cord compression is sometimes mistaken for simple muscle strain or sciatica, particularly when the patient is ambulatory and not displaying obvious neurological deficits. The Mayo Clinic notes that damage to the spinal cord frequently results in permanent alterations in strength, sensation, and other bodily functions below the injury site.

5. Venous Thromboembolism (Blood Clots)

Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), is what the CDC describes as “a frequently overlooked yet severe and preventable medical issue.” A small blood clot in the leg may be dismissed as a pulled muscle, while a pulmonary embolism — a clot that travels to the lungs — can be fatal within hours if untreated. The symptoms of PE (sudden shortness of breath, chest pain, rapid heartbeat) overlap significantly with anxiety and panic attacks, making it one of the most commonly misidentified emergencies.

Why Do Emergency Room Misdiagnoses Happen?

Emergency room misdiagnosis is rarely the result of a single error by a single physician. Instead, it typically results from a cascade of systemic, cognitive, and environmental factors that converge in the high-pressure ER setting.

Systemic and Environmental Factors

Overcrowding and understaffing are among the most significant contributors to ER diagnostic errors. When emergency departments are operating beyond capacity — which is increasingly common — physicians have less time per patient, communication breakdowns become more frequent, and critical details can be lost during shift handoffs. The American College of Emergency Physicians has repeatedly warned that ER overcrowding is a nationwide patient safety crisis.

Time pressure forces emergency physicians to make rapid decisions with limited information. Unlike a primary care physician who may see a patient over multiple visits, ER doctors often have minutes — not hours — to assess, diagnose, and initiate treatment. This environment favors quick pattern recognition, which works well for common presentations but fails when conditions present atypically.

Fragmented information compounds the problem. Emergency physicians may not have access to a patient’s full medical history, previous imaging, or medication list. When patients arrive unconscious, confused, or unable to communicate — due to language barriers, cognitive impairment, or the severity of their condition — critical diagnostic clues may be unavailable.

Cognitive Biases in Emergency Medicine

Cognitive biases account for a substantial proportion of ER diagnostic errors. The most common include:

Anchoring bias occurs when a physician fixates on an initial impression and fails to adjust the diagnosis as new information becomes available. For example, if a patient presents with chest pain and has a history of acid reflux, the physician may “anchor” on gastroesophageal reflux disease (GERD) and fail to consider a cardiac cause, even when ECG results or troponin levels suggest otherwise.

Premature closure is the tendency to stop the diagnostic process once a plausible explanation is found, without considering alternative diagnoses. This is particularly dangerous with conditions like stroke that can present with non-specific symptoms such as dizziness or headache.

Availability bias causes physicians to favor diagnoses they have encountered recently or frequently. During flu season, for example, an ER physician who has seen dozens of influenza cases may be more likely to attribute fever, body aches, and fatigue to the flu — potentially missing early sepsis or meningitis.

If you’ve ever felt that a doctor dismissed your symptoms prematurely, you may have experienced what many patients describe as medical gaslighting — and it’s more common than many people realize.

Who Is Most at Risk? Disparities in ER Misdiagnosis

Emergency room misdiagnosis does not affect all patients equally. Research consistently shows that certain populations face significantly higher risks of being misdiagnosed — and the disparities are troubling.

Women

The AHRQ report found that women face a 20–30% higher risk of being misdiagnosed in emergency departments compared with men. This disparity is particularly pronounced for cardiovascular conditions. Women’s heart attack symptoms are more likely to be attributed to anxiety or emotional distress, and studies have shown that women wait longer in ERs before receiving diagnostic testing for cardiac events. The American Medical Women’s Association has noted that heart disease has been the leading cause of death for women for over 40 years, yet gender bias in diagnosis persists.

People of Color

Research published in 2024 found that Black and Latina women face a 20–30% higher misdiagnosis rate compared with their white counterparts. Racial and ethnic disparities in emergency medicine extend beyond misdiagnosis to include differences in pain management (with studies documenting that Black patients are less likely to receive adequate pain medication), diagnostic testing, and wait times. These disparities reflect systemic biases that can lead to devastating outcomes.

Older Adults

Elderly patients present unique diagnostic challenges in the ER. They are more likely to have multiple coexisting conditions (comorbidities), take numerous medications, and present with atypical symptoms. For example, older adults experiencing a heart attack may not report chest pain at all, instead presenting with confusion, weakness, or shortness of breath — symptoms easily attributed to age or existing conditions.

Children

Pediatric patients face their own set of misdiagnosis risks. Young children cannot articulate their symptoms, and many serious pediatric conditions — including meningitis, appendicitis, and sepsis — can initially present with vague symptoms like fever, irritability, or poor feeding. Pediatric misdiagnosis remains an underappreciated but significant concern in emergency medicine.

The Consequences of ER Misdiagnosis: Beyond the Initial Error

The consequences of an emergency room misdiagnosis extend far beyond the initial visit. When a serious condition is missed, the resulting harm cascades through every aspect of a patient’s life.

Physical Harm

The most immediate consequence is medical: a missed stroke can result in permanent brain damage and disability. A misdiagnosed heart attack can lead to heart failure. An undetected aortic dissection can be rapidly fatal. The AHRQ data showing 370,000 patients suffering permanent disability or death annually from ER diagnostic errors underscores the physical toll.

Financial Impact

Misdiagnosis creates significant financial burdens. Patients may incur costs for treating the wrong condition, followed by additional costs when the correct diagnosis is eventually made — often at a more advanced stage requiring more intensive (and expensive) treatment. According to research on the cost of diagnostic errors, misdiagnosis-related spending adds billions of dollars to annual U.S. healthcare expenditures.

Psychological and Emotional Toll

The emotional impact of being misdiagnosed should not be underestimated. Many patients report feelings of anger, betrayal, anxiety, and a profound loss of trust in the healthcare system. When symptoms persist after a misdiagnosis, patients may question their own perceptions — wondering if the problem is “all in their head” — particularly if they have been told their symptoms are due to stress or anxiety.

How to Protect Yourself From ER Misdiagnosis: A Patient Advocacy Guide

While you cannot eliminate the risk of emergency room misdiagnosis entirely, you can take meaningful steps to protect yourself and your family. Being an informed, proactive patient is your strongest defense against diagnostic errors.

Before an Emergency Happens

Maintain an up-to-date medical summary. Keep a written or digital record of your medical history, current medications (including dosages), allergies, previous surgeries, and any ongoing conditions. Having this information readily available when you arrive at the ER helps physicians make faster, more accurate diagnoses. Learn how to request your medical records so they’re available when you need them.

Know your family medical history. Conditions like heart disease, stroke, blood clotting disorders, and certain cancers have genetic components. Informing ER staff of your family history can prompt them to consider diagnoses they might otherwise overlook.

During Your ER Visit

Be specific and persistent about your symptoms. Describe exactly what you’re experiencing, when it started, and how it has progressed. Don’t minimize your symptoms or defer to the physician’s initial impression if it doesn’t match what you’re feeling.

Ask the critical question: “What else could this be?” Research from Johns Hopkins Medicine suggests that asking your ER physician what other conditions could explain your symptoms encourages them to broaden their diagnostic thinking and counteracts premature closure.

Bring an advocate. If possible, bring a trusted friend or family member who can help communicate your symptoms, take notes, and ask questions on your behalf — especially if you are in significant pain or distress.

Request copies of all test results. Before you leave the ER, ask for copies of lab work, imaging results, and discharge instructions. These documents are invaluable if you need to seek a second opinion later.

After Your ER Visit

Follow up promptly. Schedule a follow-up appointment with your primary care physician or a specialist within 24–72 hours of your ER visit, especially if you were treated for a symptom-based diagnosis (such as “dizziness” or “chest pain — not cardiac”) rather than a definitive condition.

Seek a second opinion if symptoms persist or worsen. If you continue to experience the same symptoms after an ER visit — or if new symptoms develop — do not wait. Seek a second medical opinion from a different physician or specialist. Many patients who were initially misdiagnosed in the ER received their correct diagnosis through a timely second opinion.

Trust your instincts. You know your body better than anyone. If something feels wrong despite a reassuring ER diagnosis, advocate for further evaluation. The medical literature consistently shows that patient-reported symptoms and concerns are among the most valuable diagnostic tools available — when they are taken seriously.

The Future of ER Diagnostics: How AI and Technology Are Helping

Emerging technologies offer hope for reducing emergency department diagnostic errors. Artificial intelligence (AI) and machine learning systems are being developed and deployed to support ER physicians in making more accurate diagnoses.

A 2025 review published in the American Journal of Emergency Medicine examined how AI can be leveraged to reduce diagnostic errors in emergency settings. The review identified several promising applications: AI-powered clinical decision support systems that flag high-risk presentations (such as patients with dizziness who may be having a stroke), natural language processing tools that analyze clinical notes to identify missed diagnoses, and machine learning algorithms that analyze imaging results to detect subtle findings that human radiologists may overlook.

Some hospital systems have already implemented AI triage tools that assess patient symptoms upon arrival and assign risk scores for conditions like sepsis, pulmonary embolism, and acute coronary syndrome. Early data suggests these systems can reduce diagnostic delays for time-sensitive conditions.

However, AI is not a silver bullet. Experts caution that AI diagnostic tools must be rigorously validated across diverse patient populations to avoid replicating or amplifying existing biases. The goal is not to replace clinical judgment but to augment it — giving emergency physicians an additional safety net that catches potential misses. For a deeper look at how technology is transforming medical decision-making, see our guide on how AI is changing medical second opinions.

FAQ: Frequently Asked Questions About Emergency Room Misdiagnosis

How common is misdiagnosis in the emergency room?

Emergency room misdiagnosis is more common than most people realize. According to a comprehensive AHRQ report that reviewed nearly 300 studies, approximately 7.4 million diagnostic errors occur in U.S. emergency departments every year. This means roughly 1 in 18 ER patients — or about 5.7% of all emergency department visits — results in a diagnostic error. Each emergency room in the United States averages approximately 1,400 misdiagnoses per year.

What are the most dangerous conditions to be misdiagnosed in the ER?

The five most dangerous conditions to be misdiagnosed in the emergency room are stroke, heart attack (myocardial infarction), aortic aneurysm and dissection, spinal cord compression or injury, and venous thromboembolism (including deep vein thrombosis and pulmonary embolism). Together, these five conditions account for 39% of all serious misdiagnosis-related harms in emergency departments. Stroke alone is missed approximately 17% of the time, and when patients present with atypical symptoms like dizziness, the miss rate can reach 40%.

Can I sue for an emergency room misdiagnosis?

You may have legal grounds for a medical malpractice claim if an emergency room misdiagnosis caused you significant harm. To pursue a case, you typically need to demonstrate four elements: the ER physician owed you a duty of care, they breached the standard of care by making a diagnostic error that a reasonably competent physician would not have made under similar circumstances, the misdiagnosis directly caused your harm, and you suffered measurable damages as a result. Medical malpractice laws vary significantly by state and country, so consulting a qualified medical malpractice attorney is essential if you believe you were harmed by an ER diagnostic error.

Are certain groups more likely to be misdiagnosed in the ER?

Yes, research clearly demonstrates that certain populations face higher risks of emergency room misdiagnosis. Women and people of color experience a 20–30% higher misdiagnosis rate compared with white male patients, according to data from the AHRQ report and subsequent studies. Women’s cardiovascular symptoms, in particular, are more likely to be attributed to anxiety or non-cardiac causes. Older adults with multiple health conditions and children who cannot verbally communicate their symptoms are also at elevated risk for diagnostic errors in emergency settings.

What should I do if I think I was misdiagnosed in the emergency room?

If you suspect you were misdiagnosed in the emergency room, take these steps promptly: First, seek a follow-up appointment with your primary care physician or a specialist within 24–72 hours — do not wait for symptoms to worsen. Second, request complete copies of your ER medical records, including all lab results, imaging reports, and discharge notes. Third, consider seeking a second medical opinion from a different physician who can review your case with fresh eyes and access to all relevant documentation. Fourth, document your symptoms in writing, including when they started, how they have changed, and any new symptoms that have developed since your ER visit. If the misdiagnosis caused serious harm, consult a medical malpractice attorney to understand your legal options.

If you are currently experiencing a medical emergency, call 911 (US), 999 (UK), or 000 (Australia) immediately. This article is not a substitute for emergency medical care.