Medicare Part B covers doctor visits, outpatient care, and preventive services — and whether you need it depends on your age, income, and other coverage

If you are 65 or older, you are automatically enrolled in Medicare Part A (hospital insurance) when you turn 65. Medicare Part B is different: it is optional, but most people need it. Part B pays for doctor office visits, lab tests, X-rays, ambulance services, and preventive care like cancer screenings and vaccines. Without it, you pay the full cost of these services out of pocket.

You do not have to take Part B when you first turn 65, but waiting can cost you. If you delay enrollment without a valid reason, you pay a permanent penalty — a percentage added to your Part B premium for as long as you have Medicare. The penalty is 10 percent for each 12-month period you were may be able to access but did not enroll. That penalty stays with you even if you sign up later.

There are a few situations where you can delay Part B without penalty. If you are still working and covered by your employer's health plan, or if you are covered by your spouse's employer plan, you can wait. You have eight months after you leave that job or lose that coverage to enroll in Part B without penalty. If you do not take action during that window, the penalty applies.

Key Takeaways

  • Part B covers doctor visits, lab work, preventive screenings, and outpatient services that Part A does not pay for.
  • If you delay Part B enrollment after age 65 without active employer coverage, you face a permanent premium penalty of 10 percent per year of delay.
  • You have a seven-month Initial Enrollment Period centered on your 65th birthday to enroll without penalty, even if you do not need it yet.
  • If you are covered by an employer plan, you can delay Part B and enroll later during your employer coverage or within eight months of losing that coverage.
  • Part B requires a monthly premium, and you must also pay a yearly deductible and coinsurance for most services.

What Part B actually pays for

Part B covers services and supplies ordered or provided by a doctor or other may have access to provider. This includes office visits, emergency room care, urgent care, lab tests, imaging (X-rays, CT scans, ultrasounds), physical therapy, mental health services, and durable medical equipment like wheelchairs or oxygen. It also covers preventive services with no cost to you: annual wellness visits, cancer screenings, diabetes testing, bone density scans, and vaccinations.

Part B does not cover everything. It does not pay for routine dental care, eye exams for glasses or contacts, hearing aids, or most prescription drugs (those are covered under Medicare Part D). It does not cover long-term care in a nursing home, custodial care, or most services outside the United States.

When you use Part B services, you typically pay a share of the cost. You pay an annual deductible (the amount you must pay before Part B starts paying), then you pay 20 percent of the approved amount for most services. The provider bills Medicare first, and you receive a bill for your share. If the provider does not accept Medicare, you may owe more.

When you must enroll in Part B

Your Initial Enrollment Period runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after. If you enroll during this window, your coverage starts the first day of the month you turn 65 (or the month after, depending on when you enroll). This is the only time you can enroll without penalty, regardless of whether you need the coverage.

If you miss your Initial Enrollment Period and do not have a valid reason, you enter a General Enrollment Period each year from January 1 to March 31. You can enroll then, but your coverage does not start until July 1, and you pay the permanent penalty. The penalty is calculated as 10 percent of the standard Part B premium for each full 12-month period you were may be able to access but did not enroll.

If you are still working and covered by an employer health plan, you do not have to enroll in Part B during your Initial Enrollment Period. You can wait until you leave your job or lose that coverage. You then have eight months to enroll without penalty. This is called your Special Enrollment Period. You must enroll during this eight-month window or face the permanent penalty.

Part B costs and how they change

Part B has four costs: the monthly premium, the annual deductible, coinsurance, and any costs for services not covered. The standard monthly premium changes each year and is set by Medicare. In 2024, the standard premium is $164.90 per month, but your actual premium may be higher if your income is above a certain level. Higher-income beneficiaries pay an Income-Related Monthly Adjustment Amount (IRMAA) on top of the standard premium.

The annual deductible is $240 in 2024 and changes yearly. After you meet the deductible, you pay 20 percent coinsurance for most Part B services. For some services like mental health visits, you may pay a fixed copay instead. These costs add up, which is why many people also purchase a Medigap (supplemental insurance) policy to cover the deductible and coinsurance.

If you have limited income, you may be able to get help paying Part B premiums through Medicare Savings Programs run by your state. These programs can pay your premium, deductible, and coinsurance if you meet income and asset limits. Contact your state Medicaid office or call 1-800-MEDICARE to learn whether you may have access to.

Situations where you can delay Part B without penalty

You can delay Part B enrollment if you are covered by an active employer health plan — either your own job or your spouse's job. The plan must be based on current employment, not retiree coverage. If you are covered this way, you do not have to enroll in Part B during your Initial Enrollment Period. You can wait until you leave the job or the coverage ends.

Once you lose employer coverage, you have eight months to enroll in Part B. This eight-month window is your Special Enrollment Period. You must enroll during this time to avoid the permanent penalty. If you miss this window, you cannot enroll again until the next General Enrollment Period (January 1 to March 31), and the penalty will explore.

If you are a federal employee or railroad retiree, different rules may explore. Contact your employer's benefits office or the Railroad Retirement Board to understand your enrollment important date. If you are covered by Veterans benefits or TRICARE (military health coverage), you may also have different options.

How to enroll in Part B

If you are already receiving Social Security benefits when you turn 65, you are automatically enrolled in Part A and Part B. You do not have to do anything. Your Part B coverage starts on the first day of the month you turn 65, and your premium is deducted from your Social Security check.

If you are not yet receiving Social Security, you must enroll in Part B yourself. You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. You will need your Social Security number and proof of citizenship or legal residency. Enrollment takes about 10 minutes online.

If you miss your Initial Enrollment Period and need to enroll later, you can do so during the General Enrollment Period (January 1 to March 31 each year). Coverage starts July 1 of that year. If you have a Special Enrollment Period because you lost employer coverage, you can enroll anytime during your eight-month window, and coverage starts the first of the month after you enroll.

Part B and other coverage: how they work together

If you have retiree health coverage from a former employer, you can keep it and also have Part B. The two coordinate: Medicare pays first (as the primary payer), and your retiree plan may pay some of your remaining costs. Check with your former employer's benefits office to understand how they coordinate.

If you have Medicaid (state health coverage for low-income people), you can have both Medicaid and Part B. Medicaid can help pay your Part B premium and your cost-sharing (deductible and coinsurance). If you think you may be may be able to access for Medicaid, contact your state Medicaid office.

If you have TRICARE (military health coverage), you must enroll in Part B when you turn 65 to keep TRICARE coverage. If you do not enroll, TRICARE ends. If you have Veterans benefits, you can have both VA coverage and Part B, but they do not coordinate — each pays separately for services in their network.

Frequently Asked Questions

What happens if I turn 65 and do not enroll in Part B?

If you do not enroll during your Initial Enrollment Period (seven months centered on your 65th birthday) and you do not have employer coverage, you can still enroll later. But you will pay a permanent 10 percent penalty on your Part B premium for each year you delayed. That penalty stays with you for life, even if you later enroll.

Can I drop Part B after I enroll?

Yes, you can drop Part B, but you should understand the consequences. If you drop it and later want to re-enroll, you will face the permanent penalty unless you have a valid reason (like employer coverage or moving out of the country). Most people should not drop Part B once they have it.

Do I need Part B if I have a Medigap policy?

Yes. Medigap (supplemental insurance) is designed to work alongside Part B. Medigap covers some of the costs that Part B does not — like deductibles and coinsurance — but it does not replace Part B. You must have Part B to purchase a Medigap policy.

What if I am still working at 65 and have employer health coverage?

You can delay Part B without penalty. You do not have to enroll during your Initial Enrollment Period. When you leave your job or lose that coverage, you have eight months to enroll in Part B without penalty. If you miss that eight-month window, the permanent penalty applies.

How do I know if my employer plan qualifies for the Special Enrollment Period?

Your plan must be based on current employment — meaning you or your spouse is actively working. Retiree plans do not count. Ask your employer's benefits office whether your plan qualifies. If it does, they should provide written confirmation that you can use when you enroll in Part B later.