How Common Are Medical Mistakes?


They are too common. Although exact estimates are difficult to find, it is not surprising that an industry as stretched, complex, and burdened as the medical industry is fraught with errors. Many errors go unreported and tracking their exact prevalence is difficult. Nevertheless, bearing in mind that about 2.5 million deaths occur annually in the USA, here are some of the statistics and death rate estimates from various reports:

  • 42% of people believed they had personally experienced a medical mistake (NPSF survey)
  • 44,000 to 98,000 deaths annually from medical errors (Institute of Medicine)
  • 225,000 deaths annually from medical errors including 106,000 deaths due to "nonerror adverse events of medications" (Starfield)
  • 180,000 deaths annually from medication errors and adverse reactions (Holland)
  • 20,000 annually to 88,000 deaths annually from nosocomial infections
  • 2.9 to 3.7 percent of hospitalizations leading to adverse medication reactions
  • 7,391 deaths resulted from medication errors (Institute of Medicine)
  • 2.4 to 3.6 percent of hospital admissions were due to (prescription) medication events (Australian study)

Various studies have been performed about medical errors. A phone survey by the National Patient Safety Foundation found that 42% of people believed they had experienced a medical error personally or to a relative or friend. The Institute of Medicine (IOM) reports on two studies estimating the hospital deaths due to medical errors at 44,000 to 98,000 annually, which would place medical errors in the top ten causes of death in the USA. Barbara Starfield's article in JAMA places the estimates even higher, citing a total of 225,000 deaths due to iatrogenic causes, which would place health-caused deaths as the 3rd leading cause of death in the USA. Holland et al (1997) estimates as many as 1 million patients are injured while in the hospital and approximately 180,000 die as a result, with the majority due to medication adverse reactions.

Nosocomial infections caught during a hospital stay are also common, although these are not necessarily due to an identifiable error by medical personnel. On the other hand, many nosocomial infections would be prevented if hospital staff placed greater emphasis on preventive measures such as hand washing and sterilization. Estimates of nosocomial infections are as high as 2 million case annually or about 10% of hospital patients in the USA. Death rate estimates range from 20,000 annually to 88,000 deaths annually. The cost burden may be as high as $4.5 billion annually.

IOM study: deaths from medical errors: An Institute of Medicine (IOM) study in 1999 cited two different studies placing the number of deaths due to medical error in hospitals at 44,000 and 98,000 annually in the USA. For comparison, the CDC reports that in 1999 there were roughly 2.4 million US deaths, which would mean the above estimates represent approximately 1.8% and 4.0% of deaths respectively. The CDC lists the following top ten causes of death in USA for 1999 (see deaths overview for more details):

By either estimate, the results would place deaths from medical errors clearly into the top ten causes of death at either position 5 or position 9. Furthermore, since these reports were based only on hospital admissions, the real number of deaths from medical errors in a doctor's office, such as misdiagnosis or delayed treatment, may be much higher.

The above reports were based on estimates of the rates of hospital admission that results in death from adverse events. The reports found rates of adverse events at 2.9 and 3.7 percent of hospitalizations respectively, and these were extrapolated to the annual rate of hospitalizations in the USA of 33.6 million admissions in the USA 1997. About half of these adverse events were due to errors: 58% and 53% respectively.

How common are medication errors? The IOM report gives much detailed information about deaths and adverse events due to errors in medication. The report estimates that 7,391 deaths resulted from medication errors in 1993. The IOM report cites one study finding that about 2% of hospital admissions experienced a preventable adverse drug event, although the majority were not fatal. Medication error was cited as the cause of death for 1 in 131 outpatient deaths and 1 in 854 inpatient deaths. Errors in prescription and dispensing are known but difficult to quantify. For example, the IOM report cites an Australian study for 1988-1996 finding that 2.4 to 3.6 percent of hospital admissions were due to medication events, of which 32 to 69% were preventable. For more details, see medication errors.

Surgical errors: Death rates from anesthesia in surgery have declines massively to about 1 per 200,000-300,000 cases compared to 2 per 10,000 in the early 1980s.

Starfield JAMA article: Barbara Starfield's JAMA article (Volume 284, No. 4, 2000), gives very large estimates of death due to medical treatment. A total of 225,000 deaths are attributed to various iatrogenic causes. This figure puts them at the 3rd highest cause of death, only after heart disease and cancer. With roughly 2.4 million US deaths in 1999, these estimates would put iatrogenic causes at approximately 9.3% of deaths.

However, not all of these deaths are necessarily from "mistakes" with 106,000 deaths due to "nonerror adverse events of medications". In other words, people had adverse reactions to a medication but it was not an error because they had no previous indication of a risk factor. Another 80,000 deaths are attributed to nosocomial infections, which are also not necessarily due to a particular "error" since there is always a risk of infection in hospitals. Her report also cites 12,000 deaths from unnecessary surgery, 7,000 deaths from medication errors in hospitals, and 20,000 deaths in hospitals from causes other than medication errors.

National Patient Safety Foundation Survey: The National Patient Safety Foundation (NPSF) commissioned a phone survey in 1997 to review patient opinions about medical mistakes. The findings showed that 42% of people believed they had personally experienced a medical mistake. In these cases, the error affected them personally (33%), a relative (48%), or a friend (19%).


  • National Patient Safety Foundation at the AMA: Public Opinion of Patient Safety Issues, Louis Harris & Associates, September 1997.
  • Centers for Disease Control and Prevention (National Center for Health Statistics), Deaths: Final Data for 1997. National Vital Statistics Reports: Deaths: Leading Causes for 1999. Volume 49, Number 11, October 12, 2001
  • Institute of Medicine (IOM), "To Err Is Human: Building a Safer Health System", 2000, online.
  • Barbara Starfield, MD, MPH, Is US Health Really the Best in the World?, JAMA, Volume 284, No. 4, July 26, 2000, html, PDF
  • Lazarou J, Pomeranz BH, Corey PN. Incidence of adverse drug reactions in hospitalized patients: a meta-analysis of prospective studies. JAMA 1998 Apr 15;279(15):1200-5, html, PDF
  • JAMA / volume:279 (page: 1216) Drugs and Adverse Drug Reactions: How Worried Should We Be? David W. Bates, MD, MSc April 15, 1998 html, PDF
  • EILEEN G. HOLLAND, PHARM.D., and FRANK V. DEGRUY, M.D. Drug-Induced Disorders, Volume 15, No. 7, November 1, 1997, html
  • Phillips DP, Christenfeld N, Glynn LM. Lancet 1998 Feb 28;351(9103):643-4 Increase in US medication-error deaths between 1983 and 1993. medline
  • National Academies, "Preventing Death and Injury From Medical Errors Requires Dramatic, System-Wide Changes" November 29, 1999, (press release)
  • Richard J. Bonnie, Carolyn E. Fulco, Catharyn T. Liverman, Editors; Committee on Injury Prevention and Control, Institute of Medicine, Reducing the Burden of Injury: Advancing Prevention and Treatment, online
  • Schuster M, McGlynn E, Brook R. How good is the quality of health care in the United States? Milbank Q. 1998;76:517-563.

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