Some Americans do not qualify for government-provided health insurance, are not provided health insurance by an employer, and are unable to afford, cannot qualify for, or choose not to purchase, private health insurance. When charity or "uncompensated" care is not available, they sometimes simply go without needed medical treatment. This problem has become a source of considerable political controversy on a national level.

A report from the Institute of Medicine of the National Academies states: "Lack of health insurance causes roughly 18,000 unnecessary deaths every year in the United States." [27] A 2009 Harvard study published in the American Journal of Public Health found more than 44,800 excess deaths annually in the United States associated with uninsurance.[28][29] Johns Hopkins University professor Vicente Navarro stated, more broadly, in 2003, "the problem does not end here, with the uninsured. An even larger problem is the underinsured" and "The most credible estimate of the number of people in the United States who have died because of lack of medical care was provided by a study carried out by Harvard Medical School Professors David Himmelstein and Steffie Woolhandler (New England Journal of Medicine 336, no. 11 [1997]). They concluded that almost 100,000 people died in the United States each year because of lack of needed care—three times the number of people who died of AIDS."[30]

A study published in the American Journal of Public Health in 2009 found that "[u]ninsurance is associated with mortality. The strength of that association appears similar to that from a study that evaluated data from the mid-1980s, despite changes in medical therapeutics and the demography of the uninsured since that time."[46] The study estimated that lack of insurance is associated with 45,000 deaths annually.[46] This is two and a half times higher than an estimate produced by the Institute of Medicine in 2002.[47] One of the authors characterized the results as "now one dies every 12 minutes."