Medicare Eligibility Requirements: Who Qualifies and When

Medicare eligibility comes down to three things: age, citizenship, and work history. But the details matter — especially the difference between qualifying for premium-free Part A and having to pay for it, which can mean the difference between $0 and $565 per month in 2026.

The Basic Requirements

Age 65 or older is the standard threshold. You're eligible starting the first day of the month you turn 65 (or one month earlier if your birthday falls on the 1st).

Citizenship or residency: You must be a U.S. citizen or a lawful permanent resident who has lived in the United States continuously for at least five years.

Work credits for premium-free Part A: If you or your spouse earned at least 40 Social Security work credits (roughly 10 years of payroll-tax-paying employment), Part A hospital insurance is premium-free. About 99% of Medicare beneficiaries qualify this way.

Under-65 Eligibility

Medicare isn't just for seniors. You also qualify if you:

• Received Social Security Disability Insurance (SSDI) for 24 months — Medicare starts automatically in month 25
• Have End-Stage Renal Disease (ESRD) — eligibility begins with dialysis or a kidney transplant, regardless of age
• Have ALS (Lou Gehrig's disease) — Medicare starts the same month your SSDI benefits begin, with no 24-month waiting period

What "Medicare Entitlement" Actually Means

Entitlement is a legal term that matters more than most people realize. Being "entitled to" Medicare means you've met all eligibility criteria and your coverage is active — not just that you qualify to sign up.

This distinction creates real consequences in two places:

HSA contributions stop at entitlement. The IRS prohibits Health Savings Account contributions once you're entitled to any part of Medicare, including premium-free Part A. If you apply for Part A after age 65, coverage backdates up to six months automatically. Any HSA contributions during that retroactive window become excess contributions subject to a 6% excise tax.

Secondary insurance coordination changes at entitlement. Once you're entitled to Medicare, commercial insurers treat Medicare as the primary payer — even if you haven't enrolled. If you're over 65 without Part B and your non-employer insurance pays a claim, they can retroactively deny it as if Medicare should have been primary, leaving you with up to 80% of the bill.

What If You Don't Have 40 Work Credits?

If neither you nor your spouse earned 40 credits, you can still get Part A — you'll just pay a monthly premium:

• 30–39 credits: $329/month in 2026
• Fewer than 30 credits: $565/month in 2026

Part B (medical insurance) has no work-credit requirement. Everyone who meets the age and citizenship criteria can enroll in Part B by paying the standard monthly premium ($202.90 in 2026), regardless of work history.

Checking Your Eligibility

Log in to your my Social Security account at ssa.gov to verify your work credits and check whether you'll qualify for premium-free Part A. If you don't have an online account, call SSA at 1-800-772-1213.

For a complete walkthrough of how eligibility connects to enrollment timing, penalty avoidance, and plan selection, the Medicare Enrollment Guide covers every scenario from straightforward sign-ups to complex transitions from employer coverage.

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