Medicare is available to most people over 65, but it’s not automatic for everyone. Your eligibility and what you pay depend on your work history, citizenship status, and income. The majority of Americans turning 65 qualify for premium-free hospital coverage (Part A) because they or a spouse paid Medicare taxes for at least 10 years. If you don’t meet that threshold, you can still get Medicare, but you’ll pay a monthly premium for it.
Who Gets Medicare at 65 Without Paying a Premium
To qualify for premium-free Part A, you need to be 65 or older and have earned at least 40 quarters of coverage, which works out to roughly 10 years of paying into Social Security through payroll taxes. Your spouse’s work history counts too. If your spouse earned those 40 quarters, you’re eligible for premium-free Part A even if you never worked yourself.
If you’re already receiving Social Security benefits when you turn 65, you’ll be automatically enrolled in Part A. You don’t need to do anything. If you haven’t yet started collecting Social Security, you’ll need to sign up on your own during your initial enrollment period, which begins three months before your 65th birthday and ends three months after it.
What Happens if You Don’t Have Enough Work History
People who haven’t accumulated 40 quarters of work credits can still enroll in Medicare Part A, but they’ll pay for it. As of 2025, the premium runs up to $565 per month. That’s a significant cost, and it catches some people off guard, particularly those who spent years working abroad, caring for family, or in jobs that didn’t withhold Social Security taxes.
If you have to buy Part A and don’t sign up when you’re first eligible, there’s a late enrollment penalty: your monthly premium increases by 10%, and you pay that higher amount for twice the number of years you were eligible but didn’t enroll. So if you waited two years, you’d pay the penalty for four years.
Citizenship and Residency Requirements
U.S. citizens who meet the work history requirement qualify at 65. Lawful permanent residents (green card holders) also qualify if they’ve accumulated 40 quarters of work credits. Permanent residents who don’t have enough work credits can purchase Part A and enroll in Part B, but they must have lived continuously in the U.S. for at least five years before enrolling in Part B.
People who are in the country on temporary visas or without legal status are not eligible for Medicare.
Part B Is Optional but Penalized if You Delay
Part A covers hospital stays. Part B covers doctor visits, outpatient care, and preventive services. Most people enroll in both at 65, but Part B isn’t free for anyone. The standard monthly premium in 2025 is $185.
If you don’t sign up for Part B during your initial enrollment window and don’t have qualifying employer coverage, you’ll face a permanent penalty: an extra 10% added to your monthly premium for every full year you could have enrolled but didn’t. That penalty stays with you for life. Someone who delayed three years would pay 30% more every month for as long as they have Part B. The exception is if you had health coverage through your own or a spouse’s current employer during the delay, which qualifies you for a Special Enrollment Period without penalty.
Higher Earners Pay More
About 8% of Medicare beneficiaries pay more than the standard Part B premium because of their income. These surcharges, called income-related monthly adjustment amounts, are based on your tax return from two years prior. In 2025, individuals earning over $106,000 (or couples filing jointly above $212,000) start paying extra. At the highest bracket, individuals earning $500,000 or more pay $628.90 per month for Part B instead of the standard $185. Part D prescription drug coverage also carries income-based surcharges at the same income thresholds.
People Under 65 Who Qualify
Age 65 isn’t the only path to Medicare. Two groups qualify earlier. People who have received Social Security disability benefits for 24 months are automatically enrolled. And people with end-stage renal disease (permanent kidney failure requiring dialysis or a transplant) can enroll at any age, as long as they or a spouse meet the work history requirements. For dialysis patients, coverage typically starts on the first day of the fourth month of treatments, though it can begin sooner for those doing home dialysis training. People with ALS (Lou Gehrig’s disease) get Medicare as soon as their disability benefits begin, with no 24-month waiting period.
Medicare Doesn’t Work Abroad
One important limitation: Medicare coverage is almost entirely restricted to the United States and its territories (Puerto Rico, the U.S. Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands). It won’t pay for doctor visits, prescriptions, dialysis, or hospital stays in other countries, with only narrow exceptions for certain emergencies near the Canadian or Mexican border or on cruise ships within six hours of a U.S. port. If you’re planning to live abroad in retirement, Medicare won’t follow you.
Part D Has Its Own Penalty Too
Medicare Part D covers prescription drugs and is offered through private insurance plans. Like Part B, it carries a late enrollment penalty if you go without creditable drug coverage for 63 or more consecutive days after you’re first eligible. The penalty is 1% of the national base premium for each month you delayed, added to your premium permanently. Someone who waited 14 months would pay an extra 14% on top of their plan’s monthly premium for as long as they have Part D coverage, even if they switch to a different plan later.