This is general information, not insurance, medical, legal or financial advice. Medicare is a United States program. Its rules, costs and deadlines change and depend on your situation, so rely on official Medicare resources for decisions.
What Medicare is
Medicare is a federal health coverage program. It is mainly for people aged 65 and older, and for some younger people with certain disabilities or specific conditions. Eligibility often depends on work history or the history of a spouse, along with residency and citizenship or legal residency requirements.
Medicare is organized into lettered parts. Each part covers a different type of service, and some are provided by the government while others are sold by private companies. It helps to think of the parts less as levels and more as separate building blocks.
Part A: hospital coverage
Part A generally covers inpatient hospital stays, some skilled nursing facility care after a qualifying hospital stay, hospice care, and some home health services. Many people do not pay a monthly premium for Part A if they or a spouse paid Medicare taxes while working for long enough, though those who have not may be able to buy in.
Even with Part A, there are cost-sharing amounts, such as a deductible per benefit period and daily amounts for longer stays. The details are set by Medicare each year. Understanding inpatient care coverage in general helps clarify what hospital benefits look like.
Part B: medical coverage
Part B generally covers outpatient care and medical services, such as doctor visits, preventive services, lab tests, some medical equipment and outpatient hospital services. Most people pay a monthly premium for Part B, and there is an annual deductible, after which you typically pay a percentage of the approved amount for many services.
Part B has no built-in yearly limit on what you could pay for covered care, which is one reason people look at ways to fill the gaps. See the discussion of the Medicare supplement for one option. Some preventive care is covered with little or no cost sharing, depending on the service.
Together, Parts A and B are called original Medicare.
Part C: Medicare Advantage
Part C is the name for the Medicare Advantage option. Instead of using original Medicare directly, you enroll in a plan offered by a private company that contracts with Medicare. These plans must cover what Parts A and B cover, and many include additional benefits such as drug coverage, and sometimes dental, vision or hearing services.
Plans often use provider networks and may require referrals or prior authorization for some services. They also generally set an annual out-of-pocket maximum. The trade-offs are covered in the pros and cons of Medicare Advantage.
Choosing Part C does not mean you leave Medicare. You still have Medicare, but the private plan manages your benefits, and you typically must keep paying the Part B premium.
Part D: prescription drug coverage
Part D covers prescription drugs and is provided by private insurers. It can be a stand-alone plan added to original Medicare, or part of a Medicare Advantage plan. Each plan has a formulary, a list of covered drugs sorted into cost tiers, and its own premium and cost-sharing structure. The way prescription drugs are covered generally can help you understand formularies and tiers.
Because formularies and prices can change each year, checking your own medications during each enrollment period is generally recommended. Late enrollment may result in a penalty if you go without drug coverage for too long after becoming eligible, so it is worth learning the rules before your eligibility begins.
What about Medigap, and the other letters?
Medigap policies are also labeled by letters, but they are not “parts” of Medicare. They are private policies sold to help with costs in original Medicare. Do not confuse the letters on a supplement with Parts A through D.
Putting the pieces together
In general terms, there are two common paths.
- Original Medicare (A and B), with a separate drug plan (Part D) and, optionally, a supplement policy.
- A Medicare Advantage plan (C), which bundles A and B benefits, and often drug coverage, through one private plan.
The best path depends on health needs, the doctors you want to see, how much you value predictable costs versus a wider choice of providers, and your budget. There is no single answer, and the decision can usually be revisited in later years, although not always without limits.
Timing
People first becoming eligible at 65 typically have an initial enrollment period around their 65th birthday, covering a few months before and after. After that, there are annual periods for changing plans and, for some situations, special periods. If you are still working and have employer coverage, the rules for delaying certain parts can be different. Missing a window can mean delayed coverage or higher premiums, so check dates well in advance. How to coordinate with an employer plan is also a question for your benefits administrator.
Where to get help
Official Medicare materials and state counseling programs offer neutral guidance. Because plan details are specific, resist making a decision based on a single advertisement or a phone call you did not initiate.