Final answer:
A request for a formal review of an Action (Denial) or Adverse Plan Determination (Medicare) is known as an appeal, which allows for the re-evaluation of health insurance decisions.
Step-by-step explanation:
A request to the plan from a member or provider for a formal review of an Action (Denial) or Adverse Plan Determination (Medicare) is known as an appeal. This is a standard process in health insurance where the insured individual or the healthcare provider questions the insurance company's decision regarding the coverage of a particular medical service or treatment. The process is an essential part of the patient's rights within the healthcare system. In the case of Medicare, this is governed by specific rules and regulations ensuring that beneficiaries have the opportunity to have their case re-evaluated if they disagree with a decision made by their Medicare plan.