Medicare Part B is for people 65 and older, and some younger people with disabilities or end-stage renal disease

Medicare Part B covers doctor visits, outpatient care, medical equipment, and preventive services. You become covered at 65 if you are a U.S. citizen or permanent resident who has lived in the country for at least five years. If you are already getting Social Security or Railroad Retirement Board benefits, Medicare Part B starts automatically the month you turn 65. If you are not yet collecting those benefits, you need to sign up during your initial enrollment period — usually the three months before, the month of, and three months after your 65th birthday.

You may also be covered before 65 if you have been receiving Social Security Disability Insurance (SSDI) for 24 months, or if you have end-stage renal disease (ESRD) or amyotrophic lateral sclerosis (ALS). The rules for these groups differ slightly, and timing matters because missing your enrollment window can mean paying a penalty for the rest of your life.

Key Takeaways

  • You are covered by Medicare Part B at 65 if you are a U.S. citizen or permanent resident who has lived here for at least five years.
  • If you are already receiving Social Security or Railroad Retirement Board benefits, Part B enrollment happens automatically; if not, you must sign up during your initial enrollment period.
  • You may be covered before 65 if you have been on SSDI for 24 months, or if you have ESRD or ALS.
  • Delaying enrollment past your initial period usually means paying a higher premium for as long as you have Medicare.

Automatic enrollment if you are already on Social Security

If you are receiving Social Security retirement or disability benefits when you turn 65, Medicare Part B starts automatically on the first day of the month you turn 65. You do not need to do anything. Social Security will send you a Medicare card in the mail about two weeks before your coverage begins.

The same is true if you are on Railroad Retirement Board benefits. Your Part B coverage will begin automatically, and you will receive your card by mail. You will also start paying the Part B premium, which is deducted from your Social Security or Railroad Retirement check each month.

How to sign up if you are not yet on Social Security

If you are not yet receiving Social Security or Railroad Retirement Board benefits at 65, you must sign up for Medicare Part B yourself. Your initial enrollment period runs for seven months: the three months before the month you turn 65, the month you turn 65, and the three months after. For example, if you turn 65 in June, your enrollment period is March through September.

You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. You will need your Social Security number and proof of citizenship or permanent residency. Have your birth certificate, passport, or green card ready.

If you miss this window and do not have a valid reason to delay, you will pay a late enrollment penalty. The penalty is 10 percent of the standard Part B premium for each full year you were not signed up. This penalty stays with you for life, so signing up as soon as you are able is important.

Coverage before 65: SSDI recipients

If you have been receiving Social Security Disability Insurance (SSDI) for 24 months, you become covered by Medicare Part B automatically. The 24-month waiting period starts from the month your disability benefits began, not from when you applied. Once you have been on SSDI for 24 months, Medicare Part B coverage begins the first day of the 25th month.

You do not need to sign up; coverage is automatic. Social Security will send you a Medicare card in the mail. You will start paying the standard Part B premium unless you may have access to for a subsidy based on your income.

Coverage before 65: ESRD and ALS

If you have end-stage renal disease (ESRD) — permanent kidney failure requiring dialysis or a transplant — you are covered by Medicare Part B when ready, regardless of age. The same is true if you have amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease. You do not need to wait until 65.

To enroll, contact Social Security at 1-800-772-1213 or visit your local Social Security office. You will need medical documentation of your diagnosis. For ESRD, bring records showing you have been on dialysis for at least three months or have had a kidney transplant. For ALS, bring your diagnosis from a neurologist or other may have access to physician.

Coverage typically begins the first day of the month after Social Security receives your process and supporting documents, though the exact timing depends on when you explore and how quickly your documents are processed.

What happens if you delay enrollment

If you do not sign up for Part B during your initial enrollment period and you do not have a valid reason to delay, you will owe a late enrollment penalty. The penalty is calculated as 10 percent of the standard Part B premium for each full 12-month period you were not enrolled. This penalty is added to your premium permanently.

A valid reason to delay — called "creditable coverage" — means you had health insurance through an employer or your spouse's employer that was at least as good as Medicare. If you had such coverage and did not sign up for Part B, you can enroll without penalty during the eight-month period after that coverage ends. You will need to show proof of the coverage, such as a letter from your employer's benefits office.

If you are still working at 65 and have employer health insurance, talk to your employer's benefits office before your 65th birthday. They can tell you whether your coverage counts as creditable coverage and whether you should delay Part B enrollment.

Part B costs and what is covered

Part B has a monthly premium, an annual deductible, and a 20 percent coinsurance for most services. The premium amount changes each year and depends on your income. In 2024, the standard premium was $164.90 per month for most people, but higher-income beneficiaries pay more. The annual deductible was $240. After you meet the deductible, you typically pay 20 percent of the cost of covered services.

Part B covers doctor office visits, outpatient hospital care, medical equipment like wheelchairs and oxygen, mental health services, and preventive care such as cancer screenings and vaccinations. It does not cover routine dental, vision, or hearing care, or long-term care in a nursing home.

Frequently Asked Questions

What if I turn 65 while still working?

You can delay Part B enrollment if you have health insurance through your current employer. This is called creditable coverage. When you leave your job or lose the coverage, you have eight months to sign up for Part B without penalty. Contact your employer's benefits office to confirm your coverage qualifies.

Can I sign up for Part B after I turn 65 if I missed the important date?

Yes, you can sign up anytime after your initial enrollment period ends. However, you will owe a late enrollment penalty unless you had creditable coverage. The penalty stays on your premium for life, so it is worth signing up as soon as you realize you missed the important date.

Do I need Part B if I have a retiree health plan from my former employer?

Most retiree plans work alongside Medicare rather than instead of it. You should have both. Check with your former employer's benefits office to see whether your plan counts as creditable coverage and whether you can delay Part B enrollment without penalty.

What if I am a permanent resident but not yet a citizen?

You can enroll in Part B if you have been a permanent resident for at least five years and meet the other requirements. You will need to show your green card and proof of your arrival date in the United States.

Does Part B cover prescription drugs?

No. Part B covers some drugs given in a doctor's office or hospital setting, but not prescription medications you pick up at a pharmacy. For pharmacy coverage, you need Part D (prescription drug coverage), which you can add separately.