There are significant challenges in treating homeless people who have psychiatric disorders, because clinical appointments may not be kept, their continuing whereabouts are unknown, their medicines are not taken and monitored, medical and psychiatric histories are not accurate, and for other reasons. Because many homeless people have mental illnesses, this has presented a crisis in care.
Homeless persons often find it difficult to document their date of birth or their address. Because homeless people usually have no place to store possessions, they often lose their belongings, including their identification and other documents, or find them destroyed by police or others. Without a photo ID, homeless persons cannot get a job or access many social services. They can be denied access to even the most basic assistance: clothing closets, food pantries, certain public benefits, and in some cases, emergency shelters.
Obtaining replacement identification is difficult. Without an address, birth certificates cannot be mailed. Fees may be cost-prohibitive for impoverished persons. And some states will not issue birth certificates unless the person has photo identification, creating a Catch-22.
This problem is far less acute in countries which provide free-at-use health care, such as the UK, where hospitals are open-access day and night, and make no charges for treatment. In the US, free-care clinics, especially for the homeless do exist in major cities, but they are usually over-burdened with patients
The conditions affecting the homeless are somewhat specialized and have opened a new area of medicine tailored to this population. Skin conditions, including Scabies, are common because homeless people are exposed to extreme cold in the winter and they have little access to bathing facilities. They have problems caring for their feet and have more severe dental problems than the general population. Diabetes, especially untreated, is widespread in the homeless population. Specialized medical textbooks have been written to address this for providers.
There are many organizations providing free care to the homeless in countries which do not offer free medical treatment organised by the state, but the services are in great demand given the limited number of medical practitioners. For example, it might take months to get a minimal dental appointment in a free-care clinic. Communicable diseases are of great concern, especially tuberculosis, which spreads more easily in crowded homeless shelters in high density urban settings.
There has been an ongoing concern and studies about the health and wellness of the older homeless population, typically ages fifty to sixty four years of age, and even older, as to whether they are significantly more sickly than their younger counterparts and if they are under-served.
In 1999, Dr. Susan Barrow of the Columbia University Center for Homelessness Prevention Studies reported in a study that the "age-adjusted death rates of homeless men and women were 4 times those of the general US population and 2 to 3 times those of the general population of New York City".
In 2004, Boston Health Care for the Homeless in conjunction with the National Health Care for the Homeless Council published a medical manual called "The Health Care of Homeless Persons", edited by James J. O'Connell, M.D., specifically for the treatment of the homeless population.
In June 2008, in Boston, Massachusetts, the Jean Yawkey Place, a four-story, 77,653-square-foot (7,214.2 m2) building, was opened by the Boston Health Care for the Homeless Program. It is an entire full service building on the Boston Medical Center campus dedicated to providing health care for the homeless. It also contains a long term care facility, the Barbara McInnis House, which expanded to 104 beds, which is the first and largest medical respite program for homeless people in the United States.