What Is Medicare and How Do I Sign Up at 65?

The short answer

Medicare is the U.S. government health plan for people 65 and older. You sign up during a 7-month window that starts 3 months before the month you turn 65 and ends 3 months after. Each part covers different care, and missing your window can cost you money for the rest of your life.

What Medicare actually is

Medicare is a federal insurance program. It is not the same as the insurance you might get through a job. It has separate pieces, called "Parts," and you piece them together to get the coverage you need.

The Centers for Medicare & Medicaid Services (CMS) runs the program. You learn the rules and sign up through medicare.gov. If you already get Social Security benefits, some of the paperwork is done for you. If you do not get Social Security yet, you sign up on your own through the Social Security Administration at ssa.gov.

When you can sign up

The official window is called the Initial Enrollment Period. It runs for 7 months:

• 3 months before the month of your 65th birthday
• The month you turn 65
• 3 months after the month you turn 65

For example, say your 65th birthday is March 15. Your window opens December 1 (three months before your birthday month) and closes June 30. You want to enroll by the end of that window so coverage starts when you need it.

If you miss this window, a General Enrollment Period exists (January through March each year), but coverage may not start until July 1 of that year. Worse, a late-enrollment penalty can follow you for life. The penalty gets bigger the longer you wait. Details on medicare.gov spell out exactly how the penalty is calculated and when it stops.

What each part covers

This is where people get confused, so here is a plain table.

Part	What it covers	Do you pay a monthly premium?	Do you have to sign up yourself?
Part A	Hospital stays, skilled nursing after a hospital stay, some home health care	Usually no premium if you or your spouse paid Medicare taxes for 40+ quarters	You usually get it automatically if you already get Social Security
Part B	Doctor visits, outpatient care, preventive screenings, mental health care, some drugs you get in a clinic	Yes, the premium amount changes every year	Yes, you must sign up during your window
Part C (Medicare Advantage)	An "all-in-one" bundle that replaces Parts A and B. Many add Part D and extras. You pick a private plan approved by Medicare.	Varies by plan. You may still owe the Part B premium.	Yes, you choose a plan during a special window
Part D	Prescription drugs you fill at a pharmacy	Yes, varies by plan	Yes, you pick a plan during your window

Monthly premium amounts change every year. Check medicare.gov for the current year's costs.

What Parts A and B actually do

Part A is your hospital piece. If you need an overnight stay, an operation, or a short rehab stay at a skilled nursing facility after a hospital visit, Part A kicks in. You get it with no monthly premium if you (or your spouse) paid into the Medicare payroll tax for at least 40 quarters (10 years) over your working life. Most people who worked full-time before 65 meet this rule without thinking about it.

Part B is the "everyday" piece. Your yearly checkup, your specialist referral, bloodwork, flu shot, mental-health visit, and equipment like a walker or a CPAP machine fall under Part B. You pay a monthly premium. The amount is set each year and changes annually, so look it up on medicare.gov rather than trusting a number you saw last year.

For example, if you have a knee replacement in June, Part A covers the hospital stay. Part B covers the surgeon, the anesthesiologist, and the follow-up physical therapy sessions at the clinic.

What Part C and Part D do

Part D is the drug piece. It covers prescription medicines you pick up at a pharmacy. You choose from private plans that Medicare approves. Each plan has its own list of covered drugs, called a formulary, and its own copay tiers. There is no "one correct plan" for everyone. Your list of medicines and your budget decide what works for you.

Part C, also called Medicare Advantage, bundles Part A, Part B, and often Part D into one plan offered by a private insurer. Some of these plans also add extras like hearing or vision, but those extras are not universal and change from plan to plan and year to year. You still owe your Part B premium in most cases. You pick a Part C plan during an enrollment window. You can also switch or drop it during a separate window each year.

How Medicare fits into your retirement money plan

Medicare does not solve your health costs the way employer insurance might have. You still face deductibles, copays, and coinsurance (your share of the bill after insurance pays its part). Many people pair Original Medicare (Parts A and B) with a supplemental policy called a Medigap plan, or they choose a Part C plan that caps what they pay in a year. The right fit depends on your health, your medicines, your budget, and which plans exist in your county.

Health costs are a real line item in a retirement budget. If you are trying to figure out whether your savings can stretch across 25 or 30 years of retirement, how much you need to retire walks through the math. And if you plan to stop working before 65, the years between your last paycheck and your Medicare start date still need health coverage. Health insurance before Medicare explains your options for that gap.

When you are mapping out the age you can retire and whether your money holds up, the gap between "no more employer insurance" and "Medicare starts" matters. When Can I Retire works out the age you can retire and how ready you are today, including counting the years before Medicare and Social Security or CPP/OAS benefits begin. You can upload a benefit statement or type your numbers and see every step of the math, free.

A quick enrollment checklist

• Before you turn 64 and 9 months: Gather your Medicare card (if you get disability-based Medicare) and your current employer insurance info.
• 3 months before your 65th-birthday month: Open your ssa.gov account or log in to medicare.gov. Confirm your enrollment start date in writing.
• During your 7-month window: Decide on Part D or a Part C plan. Compare drug formularies if you take regular medicines.
• End of your window: You have coverage confirmation in hand. Note the start date in your calendar.
• Each fall: Review your Part D or Part C plan. Drug lists and premiums shift. A plan that worked two years ago may not fit now.

What if I am still working at 65?

If your employer has 20 or more workers, that group plan usually stays as your primary coverage. You may be able to delay Part B without a penalty. The official page at ssa.gov/medicare spells out the "special enrollment period" rules and the paperwork you need to prove your employer coverage is creditable (your doctor-visit and drug benefits are at least as good as Medicare's). Get it in writing from your HR department. Skipping the paperwork is the most common way people accidentally trigger a penalty.