Medicare offers prescription drug coverage to everyone with Medicare. If you do not decide to join a Medicare Prescription Drug Plan when you're first eligible, and you don't have other credible prescription drug coverage, or you don't get Extra Help, you'll likely pay a late enrollment penalty. To get Medicare drug coverage, you must join a plan run by an insurance company or other private company approved by Medicare. Each plan can vary in cost and drugs covered while many include some sort of yearly deductible.
Medicare Prescription Drug Plan (Part D). These plans (sometimes called "PDPs") add drug coverage to: Original Medicare with or without a Medicare Supplement Plan, some Medicare Cost Plans, some Medicare Private Fee-for-Service (PFFS) Plans, and Medicare Medical Savings Account (MSA) Plans.
Medicare Advantage Plan (Part C) (like an HMO or PPO) or other Medicare health plan that offers Medicare prescription drug coverage. You get all of your Medicare Part A (Hospital Insurance) and Medicare Part B (Medical Insurance) coverage, and prescription drug coverage (Part D), through these plans. Medicare Advantage Plans with prescription drug coverage are sometimes called “MA-PDs.” You must have Part A and Part B to join a Medicare Advantage Plan.
Each Medicare Prescription Drug Plan has its own list of covered drugs (called a formulary). Many Medicare drug plans place drugs into different "tiers" on their formularies. Drugs in each tier have a different cost.
A drug in a lower tier will generally cost you less than a drug in a higher tier. In some cases, if your drug is on a higher tier and your prescriber thinks you need that drug instead of a similar drug on a lower tier, you or your prescriber can ask your plan for an exception to get a lower copayment.