The health of populations—individuals, their families and communities—is determined by the complex interaction of social, political, economic, legal, cultural, historical, and biomedical factors. Of these determinants of health, income has long been recognized as one of the most important. People with higher incomes and higher socio-economic status tend to live longer, have lower rates of illness and injury, and are more likely to report that they have good or excellent health. People living in poverty have a lower life expectancy and higher rates of illness across a wide spectrum of diseases. Poor health predisposes individuals and families to homelessness, and homelessness exposes them to particular health problems. 

Those experiencing homelessness often live in conditions that adversely affect their overall short and long-term health. This also contribute to an increased mortality rate. Although deaths among individuals experiencing homelessness are occasionally due to freezing, they are mainly the result of injury and the rigors of street life. Climatic conditions, psychological strain, and exposure to communicable disease create and lead to a range of chronic and acute health problems, including injury from cold, tuberculosis, skin diseases, cardio-respiratory disease, nutritional deficiencies, sleep deprivation, musculoskeletal pain, and dental trouble. 

Being unhoused makes it difficult, and in some cases impossible, to access general health care services. Individuals experiencing homelessness are unable to obtain medical treatment without a health card (applying for government ID requires a permanent address); pay for items not covered by provincial medical or drug insurance plans; receive adequate treatment in cases where their personal appearance alarms health providers; make a health appointment (due lack of an address and phone); and receive coordinated care when comprehensive medical records are not kept in one location with one provider. 

Following treatment or hospitalization, an individual experiencing homelessness may have problems with acquiring adequate follow-ups, as there may be no place to recuperate and nobody to take the role of a caregiver. As a result, health care delivery to individuals experiencing homelessness is concentrated in emergency departments in the core of large urban centers and in the institutions set up to provide social supports. There is a need to respond to the acute and chronic health problems of this population and to redirect attention to preventive health. 

Whether as a cause or a consequence of ill health, homelessness has emerged as a fundamental health issue for Canadians. Homelessness affects a significant number of Canadians of all ages and is associated with a high burden of illness, yet the health care system may not adequately meet the needs of people experiencing homelessness. The main barriers to good health among those experiencing homelessness include a lack of adequate, safe, accessible and affordable housing that is linked to employability, community support, personal health care, and access to health services.