Amends the law on health care service prior authorizations: (1) to establish a standard by which to determine whether a health care service is “medically necessary”; (2) to require that the medical review or utilization review practices of a health plan be governed by this standard of medical necessity; (3) to require a health plan to employ a medical director who is responsible for reviewing and approving the health plan’s policies on responses to requests for prior authorization; (4) to require a health plan to establish clear written policies and procedures for prior authorization for health care services; (5) to restrict a health plan’s prior authorization requirements applying to: (A) physical medicine or rehabilitation services for a covered individual diagnosed with chronic pain; and (B) rehabilitative or habilitative services, including physical therapy, occupational therapy, and chiropractic services; (6) to provide that, under certain circumstances (including the failure of a health plan to respond to a request within certain time limits), a request for prior authorization is conclusively considered to be approved by the health plan; (7) to require a health plan to provide a procedure under which providers and covered individuals may seek retroactive authorization for health care services that are medically necessary covered benefits; and (8) to prohibit a health plan from denying coverage for a health care service merely because prior authorization was not obtained for the health care service before it was provided to a covered individual if: (A) the health care service would have been a covered benefit if prior authorization had been obtained before the health care service was provided to the covered individual; (B) a determination of medical necessity can be made after the health care service is provided; and (C) it is determined that the health care service was medically necessary. Defines “medically necessary” for use in these provisions.