Prescription Drug Coverage (Part D)
What to know
Part D is outpatient prescription drug coverage delivered by private stand-alone PDPs or MA-PDs. Plans must meet CMS standards: a formulary, pharmacy network, and coverage of at least two drugs per class (with exceptions for protected classes). Beneficiaries can request a formulary exception or tiering exception and can appeal denials through the coverage determination and redetermination process. The Extra Help (Low-Income Subsidy) program reduces premiums and cost-sharing for qualifying beneficiaries. The coverage gap ("donut hole") has been largely closed; beneficiaries generally pay a set percentage of drug costs until reaching the catastrophic threshold, after which cost-sharing drops sharply. Enrollment occurs during the Annual Enrollment Period (Oct 15–Dec 7) or the Initial Enrollment Period, and late enrollment can trigger a penalty unless the person had creditable coverage.
Traps
Questions test whether a drug is covered versus whether a plan must cover it. Protected classes (e.g., certain antipsychotics, antidepressants, antiretrovirals) have special formulary rules. The late enrollment penalty is based on months without creditable coverage, not on income. Do not confuse Extra Help with Medicaid; they are separate. Transition fills allow new enrollees to get non-formulary drugs temporarily.
Rule of thumb
If a beneficiary needs a drug not on formulary, the path is an exception request, then appeal-not automatic payment.