Poor health is both a cause and a result of homelessness. According to the National Health Care for the Homeless Council, people who are homeless are three to six times more likely to become ill than those with stable housing and three to four times more likely to die prematurely. The average life expectancy in the homeless population is estimated to be between 42 and 52 years, compared to 78 years in the general population.

For many reasons, individuals who are homeless and need medical treatment do not receive it. Barriers to health care among homeless individuals include inability to pay, lack of knowledge about where to seek treatment, lack of transportation, difficulty completing forms, and self-consciousness about appearance and hygiene when living on the streets. Consequently, many homeless people use hospital emergency departments as their primary source of health care. Underuse of preventive and primary care services leading to mostly unplanned interventions in more costly settings contributes to poor health outcomes, high health care costs, and inadequate coordination of care for this high-need population subgroup.