The monthly premium, according to the Centers for Medicare and Medicaid (CMS) is defined as:
The periodic payment to Medicare, an insurance company, or a health care plan for health care or prescription drug coverage. In a few cases, a note will say “Under Review” instead of a premium amount. This means Medicare and the company are still discussing the amount.
The Medicare Part D or Medicare Advantage plan monthly premium is dependent on the plan and service area (state for stand-alone prescription drug plans (PDP) and zip code (county) for Medicare Advantage plans (MA, MAPD, SNP)).