The 1999 estimate that started the field: at least 44,000, perhaps 98,000, deaths a year from medical errors
The Institute of Medicine scaled two chart-review studies up to 33.6 million admissions and wrote that "at least 44,000 Americans die each year as a result of medical errors", and that the number "may be as high as 98,000".
We have not finished checking this source. No judgement either way. how we score evidence
Caveat on this rating: Both figures are extrapolations from chart reviews of adverse events in two states and one year each, scaled to the whole country. The reviews were designed to count injuries from care and negligence, not to judge whether a given death would have happened without the error, so the death counts inherit that gap. The other direction: the report is the reason systematic counting of harm began, and the later studies that produced smaller, more careful numbers exist because of it.
Almost every number you have heard about deaths from medical care descends from one 1999 report, To Err Is Human.
Significant findings
The report's summary reads: "When extrapolated to the over 33.6 million admissions to U.S. hospitals in 1997, the results of the study in Colorado and Utah imply that at least 44,000 Americans die each year as a result of medical errors. The results of the New York Study suggest the number may be as high as 98,000."
It also carried a medication figure: "Medication errors alone, occurring either in or out of the hospital, are estimated to account for over 7,000 deaths annually."
The upper figure comes from a review of 30,121 New York hospital records from 1984, the Harvard Medical Practice Study. In that study 3.7 percent of admissions had an adverse event, 27.6 percent of the adverse events were due to negligence, and 13.6 percent of the events "led to death".
What this does not show
The source studies counted injuries from care, not deaths caused by error. A reviewer saw that an adverse event happened and that the patient died, not that one caused the other. An event that leads to death and an error that causes one are not the same thing, and the reviewers were not asked to separate them. The 2017 critique of the later 251,454 figure notes that even one of the original investigators expressed disquiet about these numbers. None of that makes the report wrong to have sounded the alarm: it changed how hospitals count harm, and the counting that followed is the reason the later, more careful numbers exist at all.
Worth asking
When you hear a death count from medical error, ask what was counted: injuries from care, or deaths a reviewer judged would not otherwise have happened?
Source
To Err Is Human: Building a Safer Health System — Institute of Medicine, Committee on Quality of Health Care in America (1999)
Read the source: https://doi.org/10.17226/9728
DOI: 10.17226/9728
How this was scored
- Study design
- not recorded
- Funding
- not recorded
- Published in
- not recorded
- Sample size
- not recorded
- Preregistered
- not recorded
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
We have not finished checking this source, so there is no scoring to show yet. “We have not checked this yet” and “this is disputed” are different statements, so no scored band is shown rather than a low one.
Read the full scoring rubric, including what it can't tell you.
Published September 29, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "not yet assessed". We have not finished checking this source. No judgement either way. One caveat travels with that badge: Both figures are extrapolations from chart reviews of adverse events in two states and one year each, scaled to the whole country. The reviews were designed to count injuries from care and negligence, not to judge whether a given death would have happened without the error, so the death counts inherit that gap. The other direction: the report is the reason systematic counting of harm began, and the later studies that produced smaller, more careful numbers exist because of it. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
To Err Is Human: Building a Safer Health System — Institute of Medicine, Committee on Quality of Health Care in America (1999). DOI: 10.17226/9728. The full source is linked on this page so you can read it yourself.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.