A widely cited 2016 analysis from Johns Hopkins University estimated that medical errors cause more than 250,000 deaths per year in the United States, which would make them the third leading cause of death, behind heart disease and cancer. That figure, if accepted, means roughly 9.5% of all U.S. deaths each year stem from some form of medical error. The ranking sparked immediate debate and continues to be contested, largely because medical errors don’t appear anywhere on official government mortality lists.
The Johns Hopkins Estimate
Researchers Martin Makary and Michael Daniel analyzed medical death rate data from four studies spanning 2000 to 2008, then extrapolated using 2013 hospital admission rates. Out of roughly 35.4 million hospitalizations that year, they calculated that 251,454 deaths were attributable to medical error. Published in The BMJ, their analysis placed medical errors ahead of respiratory disease (which kills about 150,000 Americans annually) and behind only heart disease and cancer.
A separate estimate, frequently cited alongside the Hopkins figure, put the number even higher: more than 200,000 to 400,000 patient deaths per year from preventable medical errors, with around 400,000 hospitalized patients experiencing some form of preventable harm annually. The range is wide because “medical error” is not a single, cleanly defined event. It includes surgical mistakes, diagnostic failures, medication mix-ups, communication breakdowns, and system-level failures that allow small problems to cascade.
Why Medical Errors Don’t Appear in Official Rankings
The CDC’s official list of leading causes of death for 2024 makes no mention of medical error. The top three are heart disease (683,491 deaths), cancer (619,876), and unintentional injuries (197,449). Rounding out the top ten are stroke, chronic lower respiratory diseases, Alzheimer’s disease, diabetes, kidney disease, chronic liver disease, and suicide.
The reason for the omission is structural. Death certificates in the United States are coded using the International Classification of Diseases (ICD-10), which categorizes deaths by the underlying disease or injury. There is no ICD-10 code for “medical error.” If a patient dies from a blood clot after surgery, the death certificate typically lists the clot or the original condition that prompted the surgery, not the fact that the clot was preventable. If a misdiagnosis delays cancer treatment, the death is recorded as cancer. The coding system captures what killed someone biologically but not whether the healthcare system failed them along the way.
This is the core of the Hopkins researchers’ argument: because the national mortality tracking system was never designed to capture errors in care delivery, medical error deaths are invisible in the data that shapes public health policy. Makary called it a blind spot, arguing that you can’t fix a problem you’re not measuring.
Where the Debate Stands
Not everyone accepts the third-place ranking. Critics point out that the Hopkins estimate relied on extrapolation from a relatively small number of studies, and that defining “medical error” is inherently subjective. A patient with terminal cancer who also receives a wrong medication may die from the cancer regardless. Deciding which deaths are truly caused by error versus contributed to by error is a judgment call, and different methodologies produce very different numbers.
Some researchers argue the true figure is lower than 250,000 because the studies Makary drew from may have over-attributed deaths to error. Others suggest the number could be higher, since many errors in outpatient settings, nursing homes, and primary care offices are never captured at all. The Hopkins analysis focused on hospital deaths, meaning it excluded the full spectrum of harm that happens outside hospital walls.
What no serious researcher disputes is that the number is large. Even conservative estimates place preventable medical deaths in the tens of thousands annually, which would still rank them among the top ten causes of death in the U.S.
Diagnostic Errors Cause the Most Harm
Among the specific types of medical error, misdiagnosis appears to be the deadliest. A 2024 cross-sectional analysis estimated that roughly 795,000 Americans suffer serious harm each year (permanent disability or death) from diagnostic errors. Three categories of disease account for about 76% of those harms: infections (34%), vascular events like strokes and blood clots (28.6%), and cancers (13.2%). These are sometimes called the “Big Three” of diagnostic error because they are common conditions where a missed or delayed diagnosis is most likely to result in death or permanent damage.
Diagnostic errors are especially difficult to prevent because they involve cognitive processes, not just procedural checklists. A surgeon leaving a sponge inside a patient is a clear, identifiable error. A doctor attributing chest pain to acid reflux when it’s actually a heart attack involves pattern recognition, time pressure, and incomplete information, all of which are harder to systematize.
The Global Picture
The problem is not unique to the United States. The World Health Organization estimates that around 1 in every 10 patients worldwide is harmed during healthcare, and more than 3 million deaths occur globally each year due to unsafe care. In low- and middle-income countries, the toll is proportionally worse: as many as 4 in 100 people die from unsafe care. The WHO estimates that patient harm reduces global economic growth by 0.7% annually.
Within wealthier nations, progress has been mixed. Programs targeting hospital-acquired conditions, such as infections from catheters or surgical sites, have reduced the number of those specific harms over the past decade. But a U.S. study evaluating one major federal program found that while hospital-acquired conditions declined, 30-day mortality did not meaningfully change. Reducing individual types of error has proven easier than reducing the overall death toll.
What the Ranking Means in Practice
Whether medical error is technically the third, fourth, or eighth leading cause of death matters less than what the numbers reveal about the healthcare system. Hundreds of thousands of Americans are harmed by preventable failures in care every year. The exact ranking depends on definitions and methodology, but the scale of the problem is consistently enormous across every serious attempt to measure it.
The practical takeaway is that the U.S. mortality tracking system was built to count diseases, not system failures. Until medical errors are systematically coded and reported on death certificates, the true number will remain an estimate, and the debate over ranking will continue. What the Hopkins study accomplished was forcing that conversation into the open, making it harder to treat preventable medical deaths as an invisible cost of receiving care.