Medicare Prescription Drug Plans, also known as Part D plans, are insurance plans offered by private insurance companies that can help pay for the cost of prescription drugs. To be eligible for a Part D plan, you must be enrolled in Medicare Part A and/or Part B. Part D plans are optional, but if you don't enroll in a Part D plan when you are first eligible and you go without creditable prescription drug coverage for 63 days or more, you may have to pay a late enrollment penalty if you decide to enroll in a Part D plan later.

Part D plans have a formulary, which is a list of covered drugs. Each plan has its own formulary, so it's important to make sure that the medications you take are covered by the plan you choose. If a medication you take is not on the plan's formulary, you may be able to ask for an exception to get the drug covered, or your doctor may be able to prescribe a similar drug that is on the formulary.

Part D plans have different premiums, deductibles, copayments, and coinsurance amounts, so it's important to compare plans and choose the one that best fits your healthcare needs and budget.