At least 1.5 million preventable adverse drug events a year, and one medication error per hospital patient per day
The Institute of Medicine, 2006: "at least 1.5 million preventable ADEs occur each year in the United States", built from 380,000 to 450,000 in hospitals, 800,000 in long-term care and 530,000 among outpatient Medicare patients.
We have not finished checking this source. No judgement either way. how we score evidence
Caveat on this rating: The 1.5 million is a sum of projections, each from a single site or a single practice scaled to the country, and the committee itself called them likely underestimates, which cuts both ways: the true figure may be higher, and no part of it is a direct national count. These are events, not deaths. The other direction: medication harm is the best-documented kind of harm from care, it was the most common category in the 2023 count, and it is the kind a patient can do something about by keeping one list and asking about interactions.
Drugs are where the numbers are most solid, because a wrong drug, wrong dose or missed interaction leaves a trace in the record.
Significant findings
The Institute of Medicine's 2006 report Preventing Medication Errors wrote: "The committee estimates that at least 1.5 million preventable ADEs occur each year in the United States." An ADE is an adverse drug event; the ones associated with a medication error are the preventable ones. The parts: "Hospital care, Classen and colleagues (1997) projected 380,000 preventable ADEs occurring annually, and Bates and colleagues (1995b) 450,000." "Long-term care, Gurwitz and colleagues (2005) projected 800,000 preventable ADEs." "Ambulatory care, Among outpatient Medicare patients alone, Gurwitz and colleagues (2003) projected 530,000 preventable ADEs." The committee called each of these likely an underestimate.
Its other line is the one to remember: "on average, a hospital patient is subject to at least one medication error per day".
The hospital figure traces to a 1995 study of 4,031 admissions at two Boston hospitals: 6.5 adverse drug events per 100 admissions, 28 percent of them preventable, 42 percent of the serious and life-threatening ones preventable, and the errors made mostly at ordering (56 percent) and administration (34 percent). Outside hospital, among 30,397 person-years of older Medicare patients in one practice, adverse drug events ran at 50.1 per 1,000 person-years, 27.6 percent preventable, concentrated at prescribing and monitoring.
What this does not show
These are harms from drugs where an error was involved, not deaths. Three single-site studies each carry a national number. The 1.5 million is events; the 251,454 in the previous stop is deaths, but it was built out of events, and the two must not be added or compared. An error, by the FDA's own definition, "may or may not result in an adverse event"; most cause none.
Worth asking
Which of my medicines are being checked against each other, and by whom, at every step from prescribing to the dose in my hand?
Source
Preventing Medication Errors — Institute of Medicine, Committee on Identifying and Preventing Medication Errors (2006)
Read the source: https://doi.org/10.17226/11623
DOI: 10.17226/11623
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: The 1.5 million is a sum of projections, each from a single site or a single practice scaled to the country, and the committee itself called them likely underestimates, which cuts both ways: the true figure may be higher, and no part of it is a direct national count. These are events, not deaths. The other direction: medication harm is the best-documented kind of harm from care, it was the most common category in the 2023 count, and it is the kind a patient can do something about by keeping one list and asking about interactions. 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?
Preventing Medication Errors — Institute of Medicine, Committee on Identifying and Preventing Medication Errors (2006). DOI: 10.17226/11623. 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.