Medicare has four separate parts, and most people need more than one

Medicare Part A covers hospital stays, skilled nursing care after a hospital stay, hospice, and some home health services. Part B covers doctor visits, outpatient care, and medical equipment. Part D covers prescription drugs. Part C, also called Medicare Advantage, is an alternative to Parts A and B — it bundles hospital and doctor coverage into one plan run by a private insurance company, and usually includes prescription drug coverage too.

Most people turning 65 get Part A and Part B automatically. Part D is separate and you choose it. Part C is optional — you can use it instead of A and B, but not alongside them. Understanding what each part covers helps you know what gaps exist in your coverage and whether you need a supplemental plan.

Key Takeaways

  • Part A covers hospital and skilled nursing stays; Part B covers doctors and outpatient services; Part D covers prescription drugs; Part C bundles A and B into one private plan.
  • You are automatically enrolled in Part A and Part B at 65 if you have been receiving Social Security or Railroad Retirement benefits, but you must choose Part D separately.
  • Part C (Medicare Advantage) replaces Parts A and B entirely and is offered by private insurers, usually with lower monthly premiums but higher out-of-pocket costs when you use care.
  • Original Medicare (Parts A and B) has no network restrictions, so you can see any doctor who accepts Medicare, but it does not cover prescription drugs unless you add Part D.
  • Gaps exist in all Medicare options — none cover dental, vision, hearing aids, or long-term care — so many people add a Medigap supplemental plan or choose Medicare Advantage for broader coverage.

Part A: Hospital and Skilled Nursing Coverage

Part A pays for inpatient hospital care, including room, meals, and standard nursing services. It covers up to 60 days in a hospital per benefit period, with you paying a deductible for the first stay and coinsurance for days 61 through 90. If you need more than 90 days, you can use lifetime reserve days, but those are limited.

Part A also covers skilled nursing facility care — not custodial care in a nursing home, but short-term rehabilitation after a hospital stay. You must have been hospitalized for at least three consecutive days, and the care must be for the same condition you were hospitalized for. Part A covers the first 20 days fully, then you pay coinsurance for days 21 through 100.

Hospice care and some home health services are also covered under Part A if a doctor certifies you need them. Most people do not pay a monthly premium for Part A because they or their spouse paid Medicare taxes while working. If you did not work long enough to may have access to, you can buy Part A, but the monthly cost varies based on how many years you worked.

Part B: Doctor Visits and Outpatient Services

Part B covers doctor office visits, preventive care like annual wellness exams and cancer screenings, emergency room visits, and outpatient surgery. It also covers diagnostic tests, mental health services, physical therapy, and durable medical equipment like wheelchairs, walkers, and oxygen supplies.

Part B requires a monthly premium, which changes each year. You also pay a yearly deductible before Part B starts paying, and then you typically pay 20 percent of the cost for most services after that. Some preventive services have no cost-sharing — you pay nothing for them — but most other services do.

Part B does not cover routine dental work, eye exams for glasses, hearing aids, or most outpatient prescription drugs. Those gaps are why many people add Part D for drugs and a Medigap plan to cover the 20 percent coinsurance Part B leaves with you.

Part D: Prescription Drug Coverage

Part D is a separate prescription drug plan you choose from private insurers. It is not automatic — you must enroll during your initial enrollment period or during the annual open enrollment period in the fall. If you do not choose a plan when you first become may be able to access, you may pay a penalty if you enroll later.

Part D plans vary widely in which drugs they cover, what you pay at the pharmacy, and which pharmacies you can use. Most plans have a monthly premium, a yearly deductible, and then tiered copays or coinsurance depending on the drug. Some drugs are covered fully; others require you to try a cheaper alternative first.

You can change your Part D plan once a year during open enrollment, so if your drugs are not covered well or your costs are high, you can switch. If you have low income, you may be able to get help paying Part D premiums and out-of-pocket costs through the Low-Income Subsidy program.

Part C: Medicare Advantage as an Alternative to Parts A and B

Part C, or Medicare Advantage, is a way to get your Part A and Part B coverage through a private insurance company instead of through Original Medicare. Most Medicare Advantage plans include Part D prescription drug coverage as well, so you get hospital, doctor, and drug coverage in one plan.

Medicare Advantage plans often have lower or no monthly premiums than Original Medicare plus a Medigap plan would cost. However, they usually have higher out-of-pocket costs when you use care — higher copays, coinsurance, and deductibles. They also restrict you to a network of doctors and hospitals, so you cannot see any doctor you want the way you can with Original Medicare.

Medicare Advantage plans often include extra benefits that Original Medicare does not — dental, vision, hearing, fitness programs, or meal delivery. If you choose Part C, you cannot also use Part A and Part B or buy a Medigap plan. You can switch back to Original Medicare during the annual open enrollment period, but if you have a pre-existing condition, be aware that Medigap plans may deny you or charge more when you switch back.

Gaps in Coverage: What Medicare Does Not Pay For

No matter which combination of Medicare parts you choose, certain services are not covered. Routine dental work, dentures, and dental implants are not covered by any Medicare part. Eye exams for glasses and most hearing aids are not covered. Long-term custodial care in a nursing home or assisted living is not covered — only short-term skilled nursing care after a hospital stay.

Routine foot care, most cosmetic surgery, and experimental treatments are also not covered. Some people buy a Medigap supplemental plan to cover the gaps left by Original Medicare (Parts A and B), such as the 20 percent coinsurance you pay for doctor visits. Others choose Medicare Advantage, which sometimes includes dental and vision benefits, though the coverage is usually limited.

Long-term care insurance is a separate product you buy on your own — Medicare does not cover it at any level. If you think you may need nursing home or assisted living care in the future, you should explore long-term care insurance while you are still healthy enough to be approved.

How to Enroll and When Enrollment important date Matter

Most people are automatically enrolled in Part A and Part B at 65 if they are already receiving Social Security retirement benefits or Railroad Retirement benefits. If you are not yet receiving benefits, you must contact Social Security to enroll in Medicare. You can enroll up to three months before you turn 65, during the month you turn 65, or up to three months after.

Part D and Part C require you to actively choose a plan. You have a seven-month initial enrollment period centered on the month you turn 65. If you miss this window, you may pay a penalty for the rest of your life — a percentage added to your Part D premium or Part C premium every month you go without coverage.

Once you are enrolled, you can change your Part D plan or switch between Original Medicare and Medicare Advantage during the annual open enrollment period, which runs from October 15 through December 7 each year. Changes take effect January 1. If you move, lose your current coverage, or have a major life event, you may be able to change plans outside the annual window.

Frequently Asked Questions

Do I have to take Part B when I turn 65?

Part B is not automatic — you must enroll in it. However, if you delay enrolling and do not have other health coverage, you will pay a penalty added to your Part B premium for as long as you have Medicare. If you are still working and covered by your employer's health plan, you can delay Part B without penalty.

Can I have both Original Medicare and Medicare Advantage at the same time?

No. You must choose one or the other. If you have Original Medicare (Parts A and B), you cannot also enroll in Part C. If you switch to Medicare Advantage, your Original Medicare coverage ends. You can switch back during open enrollment, but be aware of potential penalties or coverage gaps.

What happens if I do not choose a Part D plan?

If you do not enroll in Part D when you first become may be able to access, you will pay a penalty added to your Part D premium every month you go without coverage, even if you enroll years later. The penalty is 1 percent of the national average Part D premium for each month you were without coverage. If you have creditable coverage from another source, you may not owe a penalty.

Does Medicare cover my prescriptions?

Only if you enroll in Part D or choose a Medicare Advantage plan that includes drug coverage. Original Medicare (Parts A and B alone) does not cover outpatient prescription drugs. Part D plans vary in which drugs they cover and what you pay, so comparing plans during open enrollment is important if your medications are expensive.

What is the difference between Original Medicare and Medicare Advantage?

Original Medicare (Parts A and B) has no network — you can see any doctor who accepts Medicare. Medicare Advantage restricts you to a network and usually has higher out-of-pocket costs, but often includes dental and vision benefits and lower premiums. Original Medicare does not include drug coverage unless you add Part D separately.