What Is Medicare? Parts A, B, C & D Explained (2026)

Medicare comes in four parts, A, B, C, and D, and how you combine them decides what you pay and which doctors you can see. It's the federal health insurance program for people age 65 and older, plus some younger people with disabilities or specific conditions. This guide explains what each part covers, who qualifies, what it costs in 2026, when to sign up, and what Medicare does not pay for, so you can make the first decisions with confidence.

In this guide

Medicare runs on a few core choices, and the order they come in matters. You confirm you're eligible, decide between the two ways to receive benefits, sign up during the right window, and then handle the gaps Medicare leaves open. The sections below walk that path.

Who qualifies for Medicare

Medicare eligibility runs on age first, then on a few disability and medical paths for younger people.

You qualify at age 65 if you're a U.S. citizen or a lawful resident who has lived in the country for at least five years. Most people at 65 also qualify for premium-free Part A, because they or a spouse paid Medicare taxes for at least 40 quarters (10 years) of work.

There are three ways to get Medicare before 65, confirmed by the Centers for Medicare and Medicaid Services:

• Disability. After you've received Social Security Disability Insurance (SSDI) for 24 months, you're enrolled automatically in Parts A and B; coverage starts in the 25th month.
• ALS. A diagnosis of amyotrophic lateral sclerosis (Lou Gehrig's disease) waives the 24-month wait. Medicare starts the same month your SSDI benefits begin.
• End-stage renal disease (ESRD). Permanent kidney failure requiring dialysis or a transplant qualifies you at any age. If ESRD is your only basis for Medicare, coverage usually starts in the fourth month of dialysis.

The four parts of Medicare

The single most useful thing to understand is what each part does. The official breakdown lives on the parts of Medicare page; here is the working version.

Part A is hospital insurance. It covers inpatient hospital stays, skilled nursing facility care after a hospital stay, hospice, and some home health care. Most people pay no premium for Part A. You do pay a deductible each benefit period before it starts covering an inpatient stay.

Part B is medical insurance. It covers doctor visits, outpatient care, lab tests, durable medical equipment, ambulance services, and most preventive care. Part B has a monthly premium and an annual deductible, after which you generally pay 20% of the Medicare-approved amount for most services.

Part C is Medicare Advantage. This is not a separate benefit so much as a different way to receive Parts A and B. Private plans approved by Medicare bundle your hospital and medical coverage, almost always add drug coverage, and often include extras like routine dental or vision. In exchange, you use the plan's provider network and follow its rules.

Part D is prescription drug coverage. Private plans cover outpatient prescription drugs. You can add a standalone Part D plan to Original Medicare, or get drug coverage built into a Medicare Advantage plan.

The two ways to get Medicare

Every beneficiary picks one of two structures. This is the decision that shapes your costs, your provider access, and your paperwork for the year.

Original Medicare is the federal program directly. You get Parts A and B, you can see any provider in the country that accepts Medicare, and there's no network. Original Medicare has no annual out-of-pocket limit on its own, so most people add two things: a standalone Part D drug plan, and a Medigap (Medicare Supplement) policy that pays the deductibles and coinsurance Original Medicare leaves to you.

Medicare Advantage replaces that bundle with a single private plan. It covers everything Parts A and B cover, usually folds in Part D, and caps your in-network out-of-pocket spending. In 2026 that cap is federally limited to $9,250 for in-network services, and many plans set it lower. The tradeoff: you're limited to the plan's network, and many services require prior authorization. You cannot pair a Medigap policy with a Medicare Advantage plan.

One point that surprises people: with either path, you still pay the Part B premium. Medicare Advantage doesn't replace Part B; it's an additional way to receive those benefits, so the Part B premium continues alongside any plan premium. For a fuller comparison, see the dedicated guide linked at the end.

What Medicare costs in 2026

The Centers for Medicare and Medicaid Services announced the 2026 figures on November 14, 2025. They apply from January 1 through December 31, 2026.

A benefit period is the unit Part A uses. It begins the day you're admitted as an inpatient and ends after you've been out of a hospital or skilled nursing facility for 60 days in a row. Because a new benefit period can start later in the same year, the Part A deductible can apply more than once in twelve months.

Higher earners pay an income-related surcharge on top of the standard Part B and Part D premiums, called IRMAA. It's based on your tax return from two years earlier. In 2026, the surcharge starts above $109,000 in income for a single filer (or $218,000 for a couple) and rises in tiers; at the top tier the total Part B premium reaches $689.90 a month.

When to sign up

Timing is where Medicare costs people real money, because some penalties last for life.

Your Initial Enrollment Period is a seven-month window around your 65th birthday: the three months before the month you turn 65, that month, and the three months after. If you're already receiving Social Security, you're enrolled in Parts A and B automatically. Otherwise you sign up yourself through the Social Security Administration.

If you miss that window without other creditable coverage, the late penalties are steep and ongoing:

• Part B: your premium rises 10% for each full 12-month period you could have had Part B but didn't, and the penalty lasts as long as you have Part B.
• Part D: 1% of the national base premium is added for each month you went without creditable drug coverage, for as long as you have Part D.

There's an important exception. If you're still working at 65 and have coverage through a current employer, you can usually delay Part B and Part D without penalty and sign up later through a Special Enrollment Period. The rules around employer coverage are specific, so confirm them before you delay anything.

What Medicare doesn't cover

Knowing the gaps matters as much as knowing the coverage, because the gaps are where families get surprised.

The largest gap is long-term custodial care. Medicare pays for skilled nursing only on a short-term, post-acute basis: up to 100 days per benefit period, and only after a qualifying three-day inpatient hospital stay, per the skilled nursing facility benefit. It does not pay for ongoing help with daily activities, the kind of care most people mean by "nursing home." For that, families rely on private pay, long-term care insurance, or Medicaid.

Medicare also covers little routine dental, vision, and hearing care, and doesn't cover most care received outside the United States. Many Medicare Advantage plans add some dental and vision benefits, which is part of their appeal, but the scope varies widely by plan.

Help paying for Medicare

Several programs lower Medicare's costs for people with limited income and resources. They're underused, largely because no one tells eligible people they exist.

• Medicare Savings Programs are run by state Medicaid agencies and can pay your Part B premium, and in some cases your deductibles and coinsurance. In 2026 the resource limits are $9,950 for an individual and $14,910 for a couple.
• Extra Help (the Part D Low-Income Subsidy) lowers prescription drug premiums, deductibles, and copays. Its resource limits are higher than the Medicare Savings Program limits, so people who don't qualify for one may still qualify for the other through the drug-cost help program.
• Medigap doesn't depend on income. It caps the open-ended cost-sharing in Original Medicare. Your strongest opportunity to buy one is the six-month Medigap Open Enrollment Period that starts when you're both 65 and enrolled in Part B; during it, insurers must sell you any policy they offer regardless of your health.

If you have both Medicare and Medicaid, the two programs coordinate, and special plans exist to integrate them. See the dual-eligible guide below.

Frequently asked questions

Learn More

Choosing your coverage

• Original Medicare vs. Medicare Advantage
• Medigap (Medicare Supplement) explained
• How Medicare Part D drug coverage works
• Medicare Special Needs Plans (SNPs)
• Medicare Star Ratings and what they mean
• Switching plans and Medicare Advantage trial rights
• Reviewing your plan's Annual Notice of Change each fall
• Medicare Medical Savings Account (MSA) plans

Signing up and timing

• How to sign up for Medicare, step by step
• When to sign up for Medicare, and the late penalties
• Medicare late enrollment penalties: Parts A, B, and D
• Getting Medicare under 65 with a disability
• Medicare eligibility for immigrants and non-citizens
• How Medicare works with other insurance (and the COBRA trap)
• Medicare and FEHB for federal employees
• Medicare and your HSA (the contribution and tax-penalty trap)

Costs and help paying

• How much does Medicare cost? Every 2026 figure
• IRMAA: the high-income premium surcharge
• Medicare Savings Programs and Extra Help for drug costs
• Medicare and Medicaid: dual eligibility
• Creditable coverage and avoiding the Part D penalty
• How to pay your Medicare premium
• The Medicare Prescription Payment Plan (spreading drug costs)

What Medicare covers

• Preventive services and screenings
• Skilled nursing, home health, and hospice
• Mental health coverage
• Dental, vision, and hearing
• Physical, occupational, and speech therapy
• Durable medical equipment
• Ambulance coverage
• Cancer treatment
• Diabetes supplies, insulin, and services
• Kidney disease and ESRD
• Telehealth coverage
• Advance care planning
• Coverage when you travel abroad
• What Medicare doesn't cover, including long-term care
• Observation status and the hospital trap

Protecting yourself

• How to appeal a Medicare denial
• Spotting and reporting Medicare fraud
• Replacing a lost or stolen Medicare card

Find personalized help comparing your Medicare options and enrollment windows at brevy.com.

The information on Brevy.com is for educational purposes only and is not a substitute for professional legal, financial, or medical advice. Rules vary by state and program and change frequently. Always verify with the relevant agency or a qualified professional. Brevy is not a law firm, financial advisor, or healthcare provider.