A Medicare Supplement Insurance Plan is used with original Medicare. Any caregiver who accepts Medicare will take a Supplement because they only need to bill Medicare. Medicare pays its part (generally 80% of Medicare-covered benefits) and sends the remainder of the bill to the Supplement, which pays its part (generally 20%). It is important to note that Supplements do NOT include Prescription Drug Coverage (Part D, PDP), and for those who do not get a PDP when first eligible, there will be a penalty when they do get a PDP. (There are exceptions to this.) A Medicare Supplement does not change year to year (although the cost does generally go up, the coverage does not change).

Medicare Advantage Plans, sometimes called "Part C" or "MA Plans," are an “all in one” alternative to Original Medicare. They are offered by private companies approved by Medicare. If you join a Medicare Advantage Plan, you still have Medicare. These "bundled" plans include Medicare Part A (Hospital Insurance) and Medicare Part B (Medical Insurance), and usually Medicare drug coverage (Part D).

Medicare Prescription Drug Plan (Part D). These plans (sometimes called "PDPs") add drug coverage to Original Medicare, some Medicare Cost Plans, some Medicare Private Fee-for-Service (PFFS) Plans, and Medicare Medical Savings Account (MSA) Plans.

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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.

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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.