Medicare Guide: Eligibility, Enrollment, Costs and How to Choose Coverage

Quick answer: most people become eligible for Medicare at 65, or earlier after 24 months of Social Security disability benefits or with certain conditions. Your first chance to sign up is a seven-month Initial Enrollment Period around your 65th birthday. After that, you pick between Original Medicare (Parts A and B, usually with a Part D drug plan and often a Medigap policy) and a Medicare Advantage plan (Part C). For 2026, the standard Part B premium is $202.90 a month and the Part B deductible is $283, according to CMS.

Medicare is the federal health insurance program for people 65 and older and for some younger people with disabilities. It is run by the Centers for Medicare & Medicaid Services (CMS), while the Social Security Administration handles most enrollment. The program is old, popular and surprisingly easy to get wrong. A missed deadline can mean a penalty that lasts for life, and a plan picked in a hurry can leave a favorite doctor or an expensive prescription outside the network.

In this guide

Who Is Eligible for Medicare and When You Can Sign Up
Medicare Parts A, B, C and D at a Glance
What Medicare Costs in 2026
Original Medicare Plus Medigap vs Medicare Advantage
Choosing a Part D Plan and Checking Formularies
What Medicare Does Not Cover
Working Past 65: Employer Coverage and Medicare
Late Enrollment Penalties and How to Avoid Them
Annual Enrollment: What to Review Each Fall
Where to Get Free, Unbiased Help
FAQ
Frequently Asked Questions
Related Guides and Sources

This guide is the hub for every Medicare article on Pro Insurance Info. It walks through eligibility, the enrollment windows, the four parts, 2026 costs, the big choice between Medigap and Medicare Advantage, drug coverage, the gaps Medicare leaves, and the free counseling available in every state. Each section is short on purpose, and each points to a deeper guide where one exists. For a shorter primer on the parts alone, start with our explainer on Medicare Parts A, B, C and D.

Figures below come from Medicare.gov, CMS and the Social Security Administration as of October 2026. Amounts change every January, so check the official pages before you act. This article is general information, not insurance, legal, tax or medical advice, and it does not recommend any insurer or plan.

Table of Contents

Three groups qualify. The largest is people who are 65 or older and are U.S. citizens or permanent residents who have lived in the country for at least five years in a row. Younger people qualify after receiving Social Security or Railroad Retirement Board disability benefits for 24 months. People with end-stage renal disease (permanent kidney failure needing dialysis or a transplant) or amyotrophic lateral sclerosis (ALS) can qualify at any age, and ALS coverage starts as soon as disability benefits begin.

Eligibility and enrollment are two different things. If you already receive Social Security retirement benefits when you turn 65, you are usually enrolled in Parts A and B automatically, and your red, white and blue Medicare card arrives in the mail about three months before your birthday. Everyone else has to sign up, normally through the Social Security Administration online, by phone or at a local office.

The Initial Enrollment Period

Your Initial Enrollment Period (IEP) lasts seven months. It begins three months before the month you turn 65, includes your birthday month, and ends three months after it. Medicare.gov explains that signing up in the three months before your birthday month lets coverage begin on the first day of your birthday month. Signing up during the birthday month or later starts coverage the first day of the month after you enroll.

The General Enrollment Period

Anyone who misses the IEP and does not qualify for a Special Enrollment Period can sign up during the General Enrollment Period, which runs from January 1 to March 31 each year. Coverage then begins the month after you sign up. Penalties may apply, which we cover further down.

Special Enrollment Periods

Special Enrollment Periods (SEPs) open when your situation changes. The most common one belongs to people who keep working past 65 and have group health coverage through their own or a spouse’s current employment. They can delay Part B and sign up later without a penalty, as long as they enroll within eight months after the job or the coverage ends, whichever happens first. Our upcoming guide to the Initial Enrollment Period goes through every window month by month.

Medicare Parts A, B, C and D at a Glance

Medicare is split into lettered parts, and each one covers a different kind of care. Knowing which part pays for what makes the rest of the decisions easier.

Part	What it covers	Who runs it	Typical cost
Part A (hospital insurance)	Inpatient hospital stays, skilled nursing facility care after a qualifying stay, hospice, some home health care	Federal government	$0 premium for most people; $1,736 deductible per benefit period in 2026
Part B (medical insurance)	Doctor visits, outpatient care, preventive services, lab tests, durable medical equipment, some home health care	Federal government	$202.90 standard monthly premium and $283 yearly deductible in 2026, then usually 20% coinsurance
Part C (Medicare Advantage)	An all-in-one alternative that bundles Part A, Part B and usually Part D	Private insurers approved by Medicare	Varies by plan; you still pay the Part B premium
Part D (drug coverage)	Outpatient prescription drugs	Private insurers approved by Medicare	Varies by plan; deductible capped at $615 in 2026

The term “Original Medicare” means Parts A and B together, run directly by the federal government. You can see any doctor or hospital in the country that accepts Medicare, with no referrals needed. The trade-off is that Original Medicare has no yearly cap on what you pay out of pocket, and it does not include most drug coverage.

Medicare Advantage plans replace Original Medicare as the way you receive your Part A and Part B benefits. Most include drug coverage and many add extras, such as some dental or vision benefits. They also use provider networks, may require referrals and prior authorization, and must cap your yearly out-of-pocket spending for covered in-network services.

What Medicare Costs in 2026

Medicare is not free, even though many people pay nothing for Part A. The CMS 2026 premium fact sheet and the Medicare.gov page on what Medicare costs list the main amounts.

Part A

Most people pay no Part A premium because they or a spouse paid Medicare taxes for at least 10 years (40 quarters). People who do not qualify for premium-free Part A can buy it; Medicare.gov lists the 2026 premium as either $311 or $565 a month, depending on work history. The inpatient hospital deductible is $1,736 for each benefit period in 2026, and longer hospital or skilled nursing stays add daily coinsurance.

Part B

The standard Part B premium is $202.90 a month in 2026, up $17.90 from $185.00 in 2025, according to CMS. Its annual deductible is $283. Once that is met, you usually pay 20% of the Medicare-approved amount for most doctor services and outpatient care, with no annual ceiling under Original Medicare. If terms like deductible and coinsurance still feel slippery, our explainer on deductibles, copays and coinsurance breaks them down.

IRMAA: higher premiums at higher incomes

People with higher incomes pay an income-related monthly adjustment amount (IRMAA) on top of the standard Part B premium and their Part D plan premium. The Social Security Administration’s 2026 premium table starts the surcharge when modified adjusted gross income from two years earlier (2024 tax returns for 2026 premiums) is above $109,000 for an individual or $218,000 for a married couple filing jointly. The Part B add-on ranges from $81.20 to $487.00 a month, and the Part D add-on ranges from $14.50 to $91.00 a month. You can ask Social Security to use a more recent year if your income dropped after a life-changing event such as retirement.

Drug costs

Part D costs depend on the plan you pick. Medicare.gov says no plan may have a deductible above $615 in 2026. After the deductible, you pay 25% coinsurance until your out-of-pocket spending on covered drugs reaches $2,100, and then you pay nothing for covered drugs for the rest of the year. For 2027, Medicare.gov lists a maximum deductible of $700 and an out-of-pocket threshold of $2,400, which matters for anyone choosing a plan this fall.

Original Medicare Plus Medigap vs Medicare Advantage

The biggest decision most people face is how to receive their benefits. There are two main routes.

Route 1: Original Medicare, a Part D plan and often Medigap

Medigap, also called Medicare Supplement Insurance, is a private policy that helps pay costs Original Medicare leaves behind, such as the 20% Part B coinsurance and hospital deductibles. In most states, Medigap plans are standardized and identified by letters, so a Plan G from one insurer covers the same benefits as a Plan G from another; only the price and the company’s service differ. Massachusetts, Minnesota and Wisconsin standardize their plans differently.

This route gives you a nationwide choice of doctors and hospitals that accept Medicare and fewer surprise bills. It usually costs more in monthly premiums, because you pay for Part B, a Medigap policy and a separate drug plan.

Route 2: Medicare Advantage

A Medicare Advantage plan wraps hospital, medical and usually drug coverage into a single plan from a private insurer. Many have low or even $0 plan premiums beyond the Part B premium. Costs show up instead as copays and coinsurance when you use care, up to the plan’s out-of-pocket maximum. Networks matter a great deal: an HMO generally covers only in-network care except emergencies, while a PPO pays something for out-of-network care at a higher cost.

The timing trap with Medigap

Your Medigap Open Enrollment Period is a one-time, six-month window that starts the first month you have Part B and are 65 or older. During those months, an insurer cannot refuse to sell you a policy or charge more because of your health. Medicare.gov warns that after this window closes, insurers in most states can use medical underwriting, which means switching from Medicare Advantage back to Original Medicare with a Medigap policy later may be hard or expensive. A few states have broader protections, so check with your state insurance department.

A simple way to compare

If you travel often, split the year between two states or want to keep specific specialists, Original Medicare with Medigap tends to fit better.
If you want low monthly premiums and are comfortable with a network and prior authorization, a Medicare Advantage plan may fit.
If you take expensive medications, compare total yearly drug costs in each option, not only premiums.
If your health could change, weigh the Medigap underwriting rules before skipping Medigap at 65.

A dedicated comparison of Medicare Advantage and Medigap, plus a side-by-side look at Medigap Plans G and N, will sit under this guide.

Choosing a Part D Plan and Checking Formularies

Anyone on Original Medicare who wants drug coverage needs a stand-alone Part D plan, and people in most Medicare Advantage plans get drugs through the plan itself. Each plan has a formulary, which is its list of covered drugs. Formularies group drugs into tiers, and a lower tier usually means a lower copay or coinsurance. Plans may also apply rules such as prior authorization, step therapy (trying a cheaper drug first) or quantity limits.

The Medicare Plan Finder on Medicare.gov is the official tool for comparing plans. Enter every prescription with its dose and how often you take it, choose your preferred pharmacies, and the tool estimates total yearly cost for each plan in your area. Pay attention to these points when you compare:

Check that every drug you take is on the formulary and note its tier.
Look for restrictions such as prior authorization or quantity limits on your drugs.
Compare preferred-pharmacy prices against standard network pharmacies.
Look at the estimated yearly total, which includes premiums, the deductible and your share of drug costs.
Repeat the check every fall, because formularies and prices change each January.

People with limited income and resources may qualify for Extra Help, a federal program that lowers Part D premiums, deductibles and copays. Your drug plan or the Social Security Administration can tell you whether you qualify.

What Medicare Does Not Cover

Original Medicare leaves some large gaps, and they surprise many new enrollees. According to Medicare.gov, Original Medicare does not cover most of the following:

Routine dental care, such as cleanings, fillings, extractions and dentures
Routine eye exams for glasses and the glasses or contact lenses themselves (with limited exceptions, such as after cataract surgery)
Hearing aids and exams for fitting them
Long-term custodial care, meaning help with daily activities such as bathing and dressing when that is the only care you need
Most care received outside the United States

Many Medicare Advantage plans offer some dental, vision or hearing benefits, though the amounts and rules vary widely, so read the plan’s Evidence of Coverage before counting on them. Stand-alone dental and vision policies are another option. Long-term care is the most expensive gap for many families; Medicaid covers it for people who meet financial rules, and some people plan with private long-term care insurance. Our long-term care insurance calculator can help you think about the size of that need.

Working Past 65: Employer Coverage and Medicare

Turning 65 while still working raises a good question: do you need Medicare yet? The answer depends mostly on the size of the employer providing your group coverage.

Medicare.gov explains that if the employer has 20 or more employees, the group health plan generally pays first and Medicare pays second. In that case many people delay Part B (and sometimes Part A) without a penalty, using the Special Enrollment Period later. If the employer has fewer than 20 employees, Medicare usually pays first, and the group plan may require you to sign up for Parts A and B to keep full coverage. Ask the employer’s benefits office in writing how its plan works with Medicare.

Some points trip people up:

COBRA and retiree coverage are not based on current employment, so they do not protect you from the Part B late penalty.
Once you enroll in any part of Medicare, you can no longer contribute to a health savings account (HSA). When you sign up after 65, premium-free Part A can be backdated up to six months, so Medicare.gov suggests stopping HSA contributions six months before you apply to avoid a tax penalty.
Before dropping employer drug coverage, ask whether it counts as “creditable,” meaning it is expected to pay at least as much as standard Part D coverage. Your plan sends a notice each year.

Late Enrollment Penalties and How to Avoid Them

Penalties are permanent for most people, so they deserve attention before your 65th birthday.

Part B penalty

Medicare.gov says the Part B late enrollment penalty adds 10% to your monthly premium for each full 12-month period you could have had Part B but did not sign up. It is not a one-time fee. You generally pay it for as long as you have Part B. Someone who waited two full years beyond their IEP without qualifying coverage would pay 20% more than the standard premium every month.

Part D penalty

The Part D penalty applies if you go 63 days or more in a row without Part D or other creditable drug coverage after your IEP ends. Medicare.gov calculates it as 1% of the national base beneficiary premium ($38.99 in 2026) multiplied by the number of full uncovered months, rounded to the nearest 10 cents, and added to your premium for as long as you have drug coverage.

Part A penalty

Most people never face a Part A penalty because their Part A is premium-free. People who must buy Part A and sign up late may pay 10% more for twice the number of years they could have had it but did not enroll.

How to stay clear

Sign up during your IEP unless you have group coverage from current employment. Keep proof of employer coverage and creditable drug coverage notices. A dedicated guide to Part B and Part D penalties will explain the math in more depth.

Annual Enrollment: What to Review Each Fall

The Medicare Open Enrollment Period, often called the Annual Enrollment Period, runs from October 15 to December 7 each year, and it is open right now. Changes made during this window take effect January 1. During it you can switch from Original Medicare to Medicare Advantage or back, change Medicare Advantage plans, and join, switch or drop a Part D plan.

Plans send an Annual Notice of Change (ANOC) by September 30 that lists next year’s changes to premiums, copays, networks and formularies. Read it, then work through a short review:

Confirm your doctors, hospitals and pharmacies are still in network for next year.
Re-enter your current prescriptions in the Medicare Plan Finder and compare yearly costs.
Compare premiums, deductibles and out-of-pocket maximums, not only the monthly premium.
Note any new prior authorization rules for services you use regularly.
Check whether a change in income makes you eligible for Extra Help or a Medicare Savings Program.

People already in a Medicare Advantage plan get a second chance from January 1 to March 31, the Medicare Advantage Open Enrollment Period, when they can switch to another Advantage plan or return to Original Medicare once. Our guide to open enrollment and special enrollment periods covers the separate ACA Marketplace calendar for people under 65 in the same household.

Where to Get Free, Unbiased Help

Medicare decisions are personal, and free help is available in every state.

SHIP counselors. The State Health Insurance Assistance Program offers free, one-on-one Medicare counseling from trained staff and volunteers who do not sell insurance. The SHIP national locator lists your state’s program.
1-800-MEDICARE. Medicare’s help line (1-800-633-4227, TTY 1-877-486-2048) answers questions about coverage, claims and plans and can enroll you in a plan over the phone.
Medicare.gov. The Plan Finder, coverage lookup tool and “Medicare & You” handbook are all free online.
Social Security. The SSA handles enrollment in Parts A and B, IRMAA appeals and Extra Help applications.
State insurance departments. Each state’s department of insurance regulates Medigap policies and can answer questions about your rights in that state.

Licensed agents and brokers can also help compare plans, and many are paid by insurers through commissions. Asking which companies an agent represents is a fair question before you rely on their comparison.

FAQ

Frequently Asked Questions

Is Medicare free at 65?

Part A is premium-free for most people who worked and paid Medicare taxes for at least 10 years. Part B has a monthly premium ($202.90 standard in 2026), and Part D and Medigap plans have their own premiums, so Medicare is not free overall.

Do I have to sign up for Medicare if I am still working?

Not always. If you have group coverage from current employment at a company with 20 or more employees, you can usually delay Part B without a penalty. Smaller employers often require you to enroll, so confirm the rules with the benefits office.

Can I switch from Medicare Advantage to Original Medicare?

Yes, during the Annual Enrollment Period (October 15 to December 7) or the Medicare Advantage Open Enrollment Period (January 1 to March 31). Buying a Medigap policy after you switch may involve health questions in most states.

What is the difference between Medicare and Medicaid?

Medicare is federal health insurance based mainly on age or disability. Medicaid is a joint federal and state program based on income and resources. Some people qualify for both and are called dual eligible.

Does Medicare cover medical care outside the United States?

Original Medicare generally does not cover care outside the United States, apart from a few narrow exceptions. Some Medigap plans include limited foreign travel emergency coverage, and some Medicare Advantage plans offer it as well.

How do I sign up for Medicare?

If you are not enrolled automatically, apply through the Social Security Administration online at ssa.gov, by phone or at a local office. Drug plans and Medicare Advantage plans are joined through Medicare.gov, 1-800-MEDICARE or the plan itself.

Related Guides and Sources - section banner for Medicare Guide

These guides go deeper on topics from this hub. New Medicare guides are added here as they publish.

Sources used for this guide (checked October 2026): Medicare.gov pages on costs, enrollment periods, Part D costs and Medigap; the CMS fact sheet on 2026 Part A and Part B premiums and deductibles; the CMS final CY 2026 Part D redesign program instructions; and the Social Security Administration’s 2026 Medicare premiums page.

This guide is general information only. It is not insurance, legal, tax or medical advice, and Pro Insurance Info does not sell Medicare plans. Confirm amounts and rules with Medicare.gov, the Social Security Administration or your State Health Insurance Assistance Program before making decisions.