Successful intervention for inborn errors of metabolism (IEMs) is a triumph of modern medicine. For many of these conditions, medical foods are the cornerstone of therapy and the only effective interventions preventing disability or death. Medical foods are designed for patients with limited or impaired capacity to ingest, digest, absorb, or metabolize ordinary foods or nutrients, whereby dietary management cannot be achieved by modification of the normal diet alone. In the United States today, access to medical foods is not ensured for many individuals who are affected despite their proven efficacy in the treatment of IEMs, their universal use as the mainstay of IEM management, the endorsement of their use by professional medical organizations, and the obvious desire of families for effective care. Medical foods are not sufficiently covered by many health insurance plans in the United States and, without insurance coverage, many families cannot afford their high cost. In this review, we outline the history of medical foods, define their medical necessity, discuss the barriers to access and reimbursement resulting from the regulatory status of medical foods, and summarize previous efforts to improve access. The Advisory Committee on Heritable Disorders in Newborns and Children asserts that it is time to provide stable and affordable access to the effective management required for optimal outcomes through the life span of patients affected with IEMs. Medical foods as defined by the US Food and Drug Administration should be covered as required medical benefits for persons of all ages diagnosed with an IEM.