Medicare is the federal health insurance program that covers most Americans starting at age 65. It also covers younger people with certain disabilities and those with permanent kidney failure. The program is divided into distinct parts, each covering different types of care, and understanding how they fit together is the key to making smart enrollment decisions.
Who Qualifies for Medicare
Most people become eligible at 65. Your Initial Enrollment Period is a 7-month window that starts 3 months before your 65th birthday month and ends 3 months after it. Missing this window can result in permanent penalties on your premiums.
You can also qualify before 65 if you’ve received Social Security disability benefits for 24 months. People with end-stage renal disease (permanent kidney failure requiring dialysis or a kidney transplant) can get Medicare at any age, provided they or a spouse have worked long enough under Social Security or meet related eligibility criteria.
The Four Parts of Medicare
Medicare is split into four parts that each handle a different category of healthcare spending.
Part A is hospital insurance. It covers inpatient hospital stays, skilled nursing facility care, hospice care, and some home health services. Most people don’t pay a monthly premium for Part A because they or a spouse paid Medicare taxes during their working years. However, if you’re admitted to the hospital, you’ll pay a deductible of $1,676 per benefit period in 2025. Stays beyond 60 days come with daily coinsurance charges: $419 per day for days 61 through 90, and $838 per day if you dip into your lifetime reserve days.
Part B is medical insurance. It covers doctor visits, outpatient procedures, preventive services like screenings and vaccines, durable medical equipment (wheelchairs, walkers, hospital beds), and some home health care. Part B does require a monthly premium, and it carries an annual deductible. After the deductible, you typically pay 20% of the Medicare-approved amount for most services.
Part C, commonly called Medicare Advantage, is an alternative way to receive your Part A and Part B benefits. These are plans offered by private insurance companies that Medicare approves. They usually bundle prescription drug coverage in as well, and many include extras like dental, vision, or hearing benefits that Original Medicare doesn’t offer.
Part D covers prescription drugs. If you stick with Original Medicare (Parts A and B), you can add a standalone Part D plan to help pay for medications. As of 2025, a major change caps your total out-of-pocket drug spending at $2,000 per year, a significant reduction from previous limits.
Original Medicare vs. Medicare Advantage
This is the biggest choice you’ll make during enrollment. Original Medicare (Parts A and B together) and Medicare Advantage (Part C) are two different ways to get your coverage, and they work quite differently in practice.
With Original Medicare, you can see any doctor or go to any hospital in the country that accepts Medicare. There’s no network to worry about. The tradeoff is that Original Medicare has no cap on your out-of-pocket spending for the year. If you have a serious illness or injury, costs can climb unless you carry supplemental coverage.
Medicare Advantage plans typically require you to use doctors and hospitals within the plan’s network for non-emergency care. Some plans allow out-of-network visits at a higher cost, but your choices are more limited than with Original Medicare. The upside is that every Advantage plan includes a yearly out-of-pocket maximum. Once you hit that limit, the plan pays 100% of covered services for the rest of the year. Many plans also cover routine dental, vision exams, and hearing services that Original Medicare excludes.
Both options cover all medically necessary services. The decision often comes down to whether you value the freedom to see any provider nationwide (Original Medicare) or prefer built-in spending limits and extra benefits (Medicare Advantage).
What Medicare Does Not Cover
Original Medicare leaves some notable gaps. It does not cover long-term care, such as an extended stay in a nursing home for custodial reasons. Most dental care is excluded, including cleanings, fillings, extractions, and dentures. Eye exams for prescription glasses, hearing aids, and hearing exams for fitting them are also not covered. Cosmetic surgery, massage therapy, and routine physical exams fall outside Original Medicare’s scope as well.
These exclusions are one reason many people choose Medicare Advantage plans that bundle in dental and vision, or purchase separate supplemental policies.
Filling the Gaps With Medigap
If you choose Original Medicare, you can buy a Medigap policy (also called Medicare Supplement Insurance) from a private insurer to cover costs that Parts A and B leave behind. These policies help pay for coinsurance, copayments, and deductibles that would otherwise come out of your pocket.
Medigap plans are standardized by letter (Plan G, Plan N, and so on), and each letter covers a specific set of costs. Benefits can include the Part A hospital deductible, Part B coinsurance, skilled nursing facility coinsurance, and even emergency medical care during foreign travel. Some plans cover Part B excess charges, which are the amounts a provider can legally bill above Medicare’s approved rate.
One important detail: you cannot use a Medigap policy alongside a Medicare Advantage plan. Medigap is designed only to supplement Original Medicare. And it does not cover prescription drugs, so you’d still need a separate Part D plan for medications.
Enrollment Timing and Late Penalties
Signing up on time matters more than most people realize. Late enrollment penalties are not one-time fees. They’re permanent surcharges added to your monthly premium for as long as you have that coverage.
For Part B, the penalty is an extra 10% on your premium for every full 12-month period you were eligible but didn’t enroll. If you delayed enrollment by three years, you’d pay 30% more every month for life. The Part D penalty works similarly but calculates at 1% of the base premium per month of delay (roughly 12% per year), and it applies for as long as you have drug coverage.
If you have to buy Part A (because you or your spouse didn’t pay enough in Medicare taxes), delaying enrollment adds a 10% premium increase, though this penalty lasts for only twice the number of years you were late rather than permanently.
There are exceptions. If you’re still working at 65 and have employer-based health insurance, you generally get a Special Enrollment Period after that coverage ends, which protects you from penalties. But if you’re not covered by an employer plan and you miss your Initial Enrollment Period, the financial consequences follow you indefinitely.
How the Costs Add Up
Medicare is not free, even for people who qualify for premium-free Part A. You’ll still face the Part A hospital deductible each time you’re admitted as an inpatient. Part B charges a monthly premium, and after your annual deductible, you’re responsible for 20% of most outpatient services with no built-in spending cap.
Adding a Part D drug plan means another monthly premium, though the new $2,000 annual cap on out-of-pocket drug costs provides meaningful protection against catastrophic pharmacy bills. If you buy a Medigap policy on top of Original Medicare, that’s an additional monthly premium, but it can shield you from the unpredictable cost-sharing that Part A and Part B leave behind.
Medicare Advantage plans sometimes have $0 premiums beyond what you already pay for Part B, but they come with copays and coinsurance for individual services. The yearly out-of-pocket maximum provides a ceiling, but that limit can still be several thousand dollars depending on the plan.
The total cost of Medicare depends heavily on which path you choose, how much healthcare you use, and whether you carry supplemental coverage. For most people, budgeting for premiums, deductibles, and some level of cost-sharing is a realistic expectation regardless of the specific combination of plans.