Medicare, Explained Plainly
Medicare has its own vocabulary, and most of the printed material was written for people who already know it. This page answers the questions we hear most, in everyday language. Each statement of fact carries a small numbered mark that links to its source, so you can read the original for yourself.
General information, last reviewed October 2026. Medicare rules and costs change, so please confirm details with the sources linked here or with us.
Open Enrollment is October 15 to December 7
Each year during this period, everyone with Medicare can change their health and drug coverage for the following year.68 Changes take effect January 1, as long as the plan receives your request by December 7.6 Plans can change their costs, coverage, and networks each year, so it is worth reviewing yours.8
Your questions, answered
What are the parts of Medicare?
Original Medicare is made up of two parts: Part A, which is hospital insurance, and Part B, which is medical insurance.1 Part D is a separate prescription drug plan that you can add.1 Many people also add a Medicare Supplement (Medigap) policy.1
The alternative to Original Medicare is Medicare Advantage, sometimes called Part C. It is a plan from a private company that bundles Part A, Part B, and usually Part D into one plan.1
When can I first sign up?
Your first chance is your Initial Enrollment Period. It lasts seven months. It starts three months before you turn 65 and ends three months after the month you turn 65.2 Coverage always starts on the first of a month.2
If you miss this window, you may have to wait to sign up and pay a monthly late enrollment penalty for as long as you have Part B.2 After that, the General Enrollment Period runs January 1 through March 31 each year.2
I am still working at 65. Do I need Part B right away?
Not necessarily. If you or your spouse are still working when you turn 65, Medicare works a little differently, and you may choose to delay Part B.1
People with job-based coverage have a Special Enrollment Period that ends 8 months after the employment or the group health plan coverage ends, whichever comes first.2 COBRA does not count as group health plan coverage for this purpose, and having COBRA does not change when this window ends.2
Because the details depend on your employer’s plan, it helps to ask your benefits administrator how your coverage works with Medicare.5
What does Original Medicare cover, and what does it leave to me?
Original Medicare covers most medically necessary services and supplies and many preventive services, but it does not cover all of the costs.1 After you meet your deductible, you pay your share of costs as you receive care. There is no limit on what you can pay out of pocket in a year unless you have supplemental coverage, such as Medigap, Medicaid, or employer, retiree, or union coverage.1 If you receive a service that Medicare does not cover, you pay the full cost.1
What is the difference between Original Medicare and Medicare Advantage?
| Original Medicare (with an optional Supplement) | Medicare Advantage | |
|---|---|---|
| Doctors and hospitals | Any doctor or hospital that takes Medicare, anywhere in the U.S.1 | Doctors in the plan’s network and service area, for non-emergency and non-urgent care.1 |
| Drug coverage | Join a separate Medicare drug plan (Part D).1 | Most plans include drug coverage.1 |
| Extra benefits | A Medigap policy can help lower your share of costs.1 | Plans may offer extras such as vision, hearing, and dental.1 |
| Rules and costs | Your costs depend on your deductible and your share of each service.1 | You may need approval (prior authorization) for certain services. Costs vary by plan, and you may pay a monthly premium in addition to your Part B premium.1 |
You cannot have both a Medigap policy and a Medicare Advantage plan.4 Neither choice is right for everyone. The better fit depends on your doctors, your prescriptions, how you travel, and your budget.
What is a Medicare Supplement (Medigap) policy?
A Medigap policy is insurance from a private company that works alongside Original Medicare. Medicare pays its share of the approved amount first, and then your Medigap policy pays its share.4
You generally must have Part A and Part B to buy one. A policy covers only one person, so spouses each need their own.4 Medigap plans sold after 2005 do not include prescription drug coverage, so you would join a separate drug plan if you want it.4 Once you buy a policy, you keep it as long as you pay your premiums.4
When is the best time to buy a Medigap policy?
The best time is your Medigap Open Enrollment Period. It is a one-time, 6-month period that starts the first day of the month you are 65 or older and signed up for Part B.5 After this period, your options to buy a Medigap policy may be limited, and the policy may cost more.5
Outside of this period, federal law does not guarantee that an insurance company will sell you a policy. Some states offer additional opportunities, so it is worth checking your state’s rules.5
What happens if I wait to sign up for Part B or a drug plan?
Late enrollment penalties are added to your monthly premium. They are not a one-time fee, and they are usually charged for as long as you have that type of coverage.3
Part B: you pay an extra 10% for each year you could have signed up but did not, unless you qualified for a Special Enrollment Period.3
Part D: you pay an extra 1% for each month (12% a year) if you did not join a drug plan when you first got Medicare, or if you went 63 days or more without creditable drug coverage. You generally do not pay it if you have creditable drug coverage or qualify for Extra Help.3
Can I change my plan after I join?
Yes. Each year during Open Enrollment, October 15 to December 7, you can join, drop, or switch Medicare Advantage plans. If you have Original Medicare, you can join, drop, or switch your drug plan. You can also switch between Original Medicare and Medicare Advantage.6
If you switch to Original Medicare, you may need a separate drug plan and may want to add a Medigap policy, but there are limits on when you can add one.6
Where can I get free, unbiased help?
You can call 1-800-MEDICARE (1-800-633-4227) to talk with a real person, 24 hours a day, 7 days a week, except some federal holidays. TTY users can call 1-877-486-2048.7
State Health Insurance Assistance Programs (SHIPs) provide free health insurance counseling to help you choose a plan, review coverage, and understand costs.7 You can find yours at shiphelp.org.
We are glad to help you compare your options as well.
Questions about your own situation?
Every situation is different. Before suggesting anything, we take the time to understand your doctors, your prescriptions, and your budget.
Sources
- Medicare.gov, “How does Medicare work?”
- Medicare.gov, “When does Medicare coverage start?”
- Medicare.gov, “Avoid late enrollment penalties”
- Medicare.gov, “Learn how Medigap works”
- Medicare.gov, “When can I buy a Medigap policy?”
- Medicare.gov, “Open Enrollment”
- Medicare.gov, “Contact Medicare”
- CMS.gov, “Medicare Open Enrollment”
This page is general information drawn from the public sources above. It is not a recommendation of any plan, and it is not a substitute for advice about your own situation.