Most people qualify for Medicare by turning 65 and having enough work history to receive it without paying a monthly premium for Part A (hospital coverage). But age isn’t the only path. You can also qualify through a disability, a specific medical condition, or a spouse’s work record, and the details of how you qualify affect what you pay and when your coverage begins.
The Standard Path: Turning 65
The most common way to qualify is simply reaching age 65. Once you do, you’re eligible to enroll in Medicare Part A (hospital insurance) and Part B (medical insurance). Your Initial Enrollment Period lasts seven months: it starts three months before the month you turn 65 and ends three months after. Missing this window can mean gaps in coverage and permanent penalties on your premiums.
If you’re already receiving Social Security benefits when you turn 65, you’ll typically be enrolled in Parts A and B automatically. If you’re not collecting Social Security yet, you’ll need to sign up yourself through the Social Security Administration, either online, by phone, or at a local office.
Work Credits and Premium-Free Part A
Qualifying for Medicare and qualifying for free Part A are two different things. To get Part A without a monthly premium, you (or your spouse) need at least 40 Social Security work credits. You earn up to four credits per year, so 40 credits translates to roughly 10 years of work where Medicare taxes were deducted from your pay.
If you have fewer than 40 credits, you can still enroll in Part A, but you’ll pay a monthly premium. The amount depends on how many credits you’ve earned. In 2025, people with 30 to 39 credits pay $311 per month, while those with fewer than 30 credits pay $565 per month. That’s a significant cost, so it’s worth checking your credits through your Social Security account online before you turn 65.
Qualifying Through a Spouse’s Work Record
If you didn’t work long enough to earn 40 credits on your own, you may still qualify for premium-free Part A based on your spouse’s (or ex-spouse’s) work history. For current spouses, your partner needs to have earned at least 40 credits and be at least 62 years old. For ex-spouses, the marriage generally must have lasted at least 10 years, and you must be currently unmarried.
This applies to both hospital and medical coverage. You still need to meet the other basic requirements: be 65 or older, be a U.S. resident, and be either a U.S. citizen or a lawful permanent resident who has lived in the country for at least five continuous years.
Qualifying Under 65 With a Disability
You don’t have to wait until 65 if you’re receiving Social Security Disability Insurance (SSDI). Everyone eligible for SSDI also qualifies for Medicare, but there’s a 24-month waiting period. The clock starts from the first month you’re entitled to disability benefits, not the month you applied or were approved.
If you were previously on disability and your benefits ended, some of those earlier months may count toward the 24-month requirement. This applies if your new disability begins within 60 months of your previous benefits ending (or within 84 months for certain categories like disabled widow/widower benefits). If your current disability is the same as or directly related to your previous one, there’s no time limit on counting those earlier months.
Qualifying With ALS or Kidney Failure
Two medical conditions bypass the normal waiting periods entirely.
If you’re diagnosed with ALS (amyotrophic lateral sclerosis, also called Lou Gehrig’s disease), Medicare coverage begins the same month your SSDI benefits start. There’s no 24-month wait.
If you have end-stage renal disease (permanent kidney failure requiring regular dialysis or a kidney transplant), you can get Medicare regardless of your age. You do need to meet a work-history requirement: either you, your spouse, or a parent you depend on must have worked long enough under Social Security or as a government employee. If you’re already receiving or eligible for Social Security or Railroad Retirement benefits, that also counts.
Citizenship and Residency Requirements
Beyond age and work history, Medicare has residency rules. You must be a U.S. citizen or a lawful permanent resident (green card holder) who has lived continuously in the United States for at least five years before applying. You also need to be a current U.S. resident. These requirements apply to all parts of Medicare, whether you’re enrolling in premium-free Part A or purchasing coverage.
What Happens If You Enroll Late
Timing matters. If you delay signing up for Part B after you first become eligible and you don’t have qualifying coverage through an employer, you’ll face a late enrollment penalty that lasts for as long as you have Part B. The penalty adds 10% to your monthly Part B premium for every full 12-month period you could have been enrolled but weren’t. So if you waited three years, your premiums would be 30% higher permanently.
Part D (prescription drug coverage) has a similar penalty structure. If you go 63 or more consecutive days without creditable drug coverage after you’re first eligible, you’ll pay an extra 1% of the standard Part D premium for each month you went without coverage. That’s roughly 12% per year of delay, and like the Part B penalty, it stays with you.
The key exception: if you have health coverage through your own or a spouse’s current employer, you generally won’t face penalties for delaying Medicare enrollment. You’ll get a Special Enrollment Period to sign up once that employer coverage ends.