“CMS defines a Referral as a written OK from your primary care doctor for you to see a specialist or get certain services. In many Medicare Managed Care Plans, you need to get a referral before you can get care from anyone except your primary care doctor. If you don’t get a referral first, the plan may not pay for your care.” – www.medicare.gov

“….for some Medicare Advantage Plans, it is the permission requested from your Primary Care Physician to see a specialist and must be approved by the insurance company.”