A report by the investigative arm of the US Congress, the General Accounting Office, says federal laws and statutes in place cause funding disparities in the federal financing of health-care programmes, for insular areas, including Guam, American Samoa and the Northern Marianas.
As a result low-income families, residents with disabilities and others receive less financial support for medicine and other health-care needs than the US states.
Guam's delegate to the US Congress, Madeline Bordallo, says Guam is being treated differently and unequally.
Mrs Bordallo added this had been the case for many years and is a situation she continued to work to improve.
The GAO report looked at federal funding sources to five insular areas: American Samoa, the Northern Mariana Islands, Guam, Puerto Rico and Virgin Islands.