Medicare eligibility starts at age 65 for most Americans. That’s the standard threshold, and it hasn’t changed. But several situations allow people under 65 to qualify, and the timing of when you sign up matters more than many people realize.
The Standard Age: 65
If you’re a U.S. citizen or a permanent resident who has lived in the country for at least five continuous years, you become eligible for Medicare at 65. To get Part A (hospital coverage) without paying a monthly premium, you also need to be eligible for Social Security or Railroad Retirement Board benefits, which generally means you or your spouse paid into the system for at least 10 years of work.
If you’re already receiving Social Security benefits when you turn 65, you’ll be enrolled in Medicare Parts A and B automatically. Your coverage will begin the month you turn 65. If you haven’t started collecting Social Security yet, you’ll need to sign up yourself.
Your 7-Month Enrollment Window
The Initial Enrollment Period lasts seven months: it starts three months before the month you turn 65, includes your birthday month, and ends three months after. Signing up during the first three months means your coverage starts right when you turn 65. Waiting until the later months delays your coverage start date.
Missing this window has real financial consequences. For Part B (which covers doctor visits, outpatient care, and preventive services), the penalty is an extra 10% added to your premium for every full year you could have enrolled but didn’t. That penalty stays on your premium for as long as you have Part B, which for most people means the rest of your life. With the standard Part B premium set at $185 per month in 2025 and rising to $202.90 in 2026, even a one-year delay adds roughly $20 per month permanently.
Still Working at 65? You May Be Able to Wait
If you or your spouse are still working at 65 and have health insurance through that employer, you can delay signing up for Part B without triggering the late enrollment penalty. This only applies if the coverage is a group health plan through current employment. Retiree coverage, COBRA, and self-employed insurance plans don’t count, so if any of those describe your situation, sign up at 65.
Once you stop working or lose that employer coverage (whichever comes first), you get an eight-month Special Enrollment Period to sign up for Medicare. This window starts the day you stop working or lose coverage, not the day you decide to enroll, so don’t wait to act. One important note: even if you have employer coverage, check with your employer about whether you should enroll in Part A when you turn 65. Some employer plans expect Medicare to be your primary insurer once you’re eligible, and skipping it could leave you with unexpected bills.
Qualifying Before 65: Disability
You don’t have to wait until 65 if you’re receiving Social Security Disability Insurance (SSDI) benefits. After 24 consecutive months of receiving disability payments, you’re automatically enrolled in Medicare. The 24-month clock starts from your first disability benefit payment, not from when you applied or were approved.
There’s one major exception to the waiting period. If you have ALS (Lou Gehrig’s disease), Medicare coverage begins automatically as soon as your disability benefits start. There is no 24-month wait.
Qualifying Before 65: Kidney Failure
End-stage renal disease (ESRD), meaning permanent kidney failure requiring dialysis or a transplant, qualifies you for Medicare at any age. You need to meet a work history requirement through Social Security, Railroad Retirement, or government employment, either through your own work record or through a spouse or parent.
The timing of coverage depends on your treatment. If you’re starting dialysis, Medicare coverage typically begins on the first day of the fourth month of treatments. You can eliminate that three-month gap if you enroll in a home dialysis training program at a Medicare-certified facility during those first three months and your doctor expects you to complete it. If you’re getting a kidney transplant, coverage can start the month you’re admitted to a Medicare-certified hospital for the transplant, as long as the surgery happens that month or within the next two.
What Medicare Costs at 65
Most people pay no monthly premium for Part A because they or their spouse paid Medicare taxes during their working years. Part B, however, has a standard monthly premium: $185 in 2025, increasing to $202.90 in 2026. Higher earners pay more based on their tax returns from two years prior.
Part B also carries an annual deductible, which is $257 in 2025 and $283 in 2026. After meeting that deductible, Medicare generally covers 80% of approved services, leaving you responsible for the remaining 20% unless you have supplemental coverage. These costs are worth factoring into your retirement planning well before you turn 65, especially if you’re comparing employer insurance to Medicare.