Definitions. In this regulation, the following terms have the meanings indicated: “Medically necessary” means those services and supplies provided by a hospital, practitioner, or other provider of health care services to identify or treat an illness or injury which has been diagnosed or is reasonably suspected, and which are: Consistent with the diagnosis and treatment of the member's condition; In accordance with standards of good medical practice; Required for reasons other than the convenience of the member, practitioner, or other provider; and The most appropriate supply or level of service which can safely be provided for the member. “Reasonable cost” means the lowest of the following costs: The fee usually charged by a health care provider to all patients for a particular service or supply; The fee customarily charged by health care providers for the same service or supply in the same general area; or The actual fee charged by a health care provider to a patient for a particular service or supply. The Medicare Supplemental Program shall provide benefits as follows: Benefits or payments under the Medicare Supplemental Program shall be provided in accordance with the reasonable cost of a medically necessary service or supply. Benefits or payments under the Medicare Supplemental Program may not duplicate any benefits payable by Medicare. With respect to members eligible for Medicare, whether those members are enrolled under Part A (Hospital Insurance) or Part B (Medical Insurance) of Title XVIII of the Social Security Amendments of 1965 (Title I of Public Law 89—97), the benefits provided under the Medicare Supplemental Program shall be reduced by the amount of benefit or payment that would have been furnished the member under Title XVIII, if that member had been enrolled. Benefits furnished under Title XVIII, or that would have been furnished under Title XVIII, shall be charged against the maximum benefits provided for under the Medicare Supplemental Program. Eligible Persons. Retired employees and their spouses and dependents who are eligible for Medicare benefits and who are eligible for retired employee health benefits in accordance with Regulation .03A(10) of this chapter are eligible for benefits provided under the Medicare Supplemental Program. Effective Dates. Eligibility. At the start of the calendar month in which age 65 is reached or Medicare eligibility is otherwise established, a retired employee and eligible spouse and dependents are eligible for benefits under the Medicare Supplemental Program. Coverage. At the start of the calendar month in which age 65 is reached or Medicare eligibility is otherwise established, the retired employee's membership shall be automatically converted to an appropriate membership level under the Medicare Supplemental Program. Election of Coverage of Employees 65 Years Old or Older, and Employees' Spouses 65 Years Old or Older. Eligibility. Not later than the calendar month in which age 65 is reached, the following persons shall designate their election of coverage of the State employees' health insurance program or Medicare as their primary health insurance carrier: Eligible employees 65 years old or older, who are eligible for health benefits in accordance with Regulation .03 of this chapter; Eligible spouses 65 years old or older, of employees who are any age, and who are eligible for health benefits in accordance with Regulation .03 of this chapter. Coverage. An employee 65 years old or older, or an employee's spouse 65 years old or older, shall designate coverage under the State employees' health insurance program or Medicare. Those employees and spouses who elect coverage under the State employees' health insurance program shall receive coverage under the applicable membership as would be applicable to all other State employees and their dependents without Medicare. In accordance with applicable federal law, those employees and spouses who elect coverage under Medicare are ineligible for benefits under the Medicare Supplemental Program or other health insurance coverage available to all other State employees. Upon retirement from State service by the employee 65 years old or older, the retired employee and spouse are eligible for benefits under the Medicare Supplemental Program as applicable to all other State retired employees.