Prescription drug coverage, also known as Part D, is a Medicare benefit that helps cover the cost of prescription drugs. It is offered by private insurance companies that contract with Medicare. Enrolling in a Medicare Advantage plan with drug coverage or a stand-alone Prescription Drug Plan (PDP) can help lower out-of-pocket prescription drug costs.
Each plan has a list of covered drugs, called a formulary, and rules for getting drugs. Some plans place drugs into different “tiers” on their formularies, with different copays for each tier. In addition, plans may have “coverage gaps” or “donut holes” where you have to pay a larger share of the cost of drugs.