Medicare Part B is not automatic — you have to sign up for it, and most people pay a monthly premium

When you turn 65, you are automatically enrolled in Medicare Part A (hospital insurance). Part B (medical insurance for doctor visits and outpatient care) is different. You must actively choose to enroll in it, and you will pay a monthly premium unless you meet specific income limits. If you delay enrolling in Part B when you first become may be able to access, you may face a permanent penalty on your premium.

The confusion often comes from the word "Medicare" itself. Medicare is the federal program with four parts: A, B, D, and sometimes C. Part B is not bundled with Part A automatically. You decide whether to take it, when to take it, and whether to pair it with a Medigap policy or a Medicare Advantage plan.

Key Takeaways

  • Part A is automatic at 65; Part B requires you to sign up during your enrollment window or face a lifetime penalty.
  • Part B covers doctor visits, lab work, imaging, and outpatient procedures — things Part A does not.
  • You pay a monthly premium for Part B, which varies by income and year.
  • If you delay enrolling in Part B without a valid reason, your premium increases by 10 percent for each year you waited.
  • Most people enroll in Part B during their Initial Enrollment Period, which begins three months before the month they turn 65.

When Part B enrollment happens and what happens if you miss it

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. During this window, you can enroll in Part B without penalty, even if you do not need it yet.

If you do not enroll during those seven months and you do not have a valid reason (called a "may have access to event"), you enter what Medicare calls a General Enrollment Period. This runs from January 1 to March 31 each year. You can enroll then, but your premium will be 10 percent higher for each full year you delayed. That penalty stays with you for life — it does not go away after a few years.

A few situations let you enroll late without penalty. These include losing employer coverage, moving out of the United States and returning, or may have access to for Medicaid. If any of these explore to you, you have a two-month window to enroll after the may have access to event ends.

Who does not need Part B and who should take it anyway

If you are still working and your employer has 20 or more employees, you may be able to delay Part B without penalty. Your employer health plan is considered "creditable coverage," which means it covers at least as much as Part B does. You can stay on that plan and enroll in Part B later when you retire, as long as you enroll within eight months of losing the coverage.

If your employer has fewer than 20 employees, you should enroll in Part B when you turn 65, even if you are still working. Without Part B, Medicare will not pay its share of your medical bills, and you could face large out-of-pocket costs.

Some people with very low income may may have access to for Medicaid, which can cover Part B premiums and cost-sharing. If you think you might may have access to, contact your state Medicaid office or call 211 to find local resources. Medicaid rules vary by state.

What Part B actually covers and what it does not

Part B covers doctor office visits, preventive care (like annual wellness visits and screenings), lab work, X-rays, imaging, and outpatient surgery. It also covers durable medical equipment like wheelchairs and oxygen, and some therapy services. Part B has a yearly deductible (the amount you pay before Medicare starts paying), and then you typically pay 20 percent of the cost after that.

Part B does not cover dental, vision, hearing aids, or long-term care. It also does not cover prescription drugs — that is Part D. If you want coverage for those things, you need to add Part D (prescription drug coverage) and possibly a Medigap or Medicare Advantage plan.

How Part B premiums work and income-related adjustments

The standard Part B premium changes each year. In 2024, it was $164.90 per month for most people, but this amount increases annually. You pay the premium whether you use Part B or not.

If your income is above a certain threshold, you pay a higher premium called an Income-Related Monthly Adjustment Amount (IRMAA). Medicare uses your tax return from two years ago to calculate this. For example, in 2024, if you filed taxes as a single person and your modified adjusted gross income was above $97,000, you paid more than the standard premium. The thresholds are higher for married couples filing jointly.

If your income drops due to retirement, job loss, or divorce, you can ask Medicare to recalculate your IRMAA using your current year's income instead. You will need to submit documentation of the life event.

Part B and Medicare Advantage versus Medigap

Once you have Part B, you choose how to use it. You can pair it with a Medigap policy (also called Supplemental Insurance), which covers some of the costs that Part B does not — like the deductible and the 20 percent coinsurance. Medigap is sold by private insurance companies, and you pay a separate premium for it.

Alternatively, you can enroll in a Medicare Advantage plan (Part C), which is an all-in-one alternative to Original Medicare (Part A and B). Medicare Advantage plans are offered by private insurers and often include prescription drug coverage and dental or vision benefits. You still have Part B, but the Advantage plan becomes your main coverage. You pay a monthly premium to the plan, and you may have different copays and deductibles than Original Medicare.

You cannot have both Medigap and Medicare Advantage at the same time. You choose one path or the other. During the Annual Enrollment Period (October 15 to December 7 each year), you can switch between them.

What to ask your doctor or Medicare counselor

Before your 65th birthday, ask your doctor whether you should enroll in Part B right away or whether you can safely delay it. If you are still working, ask your employer's benefits department whether your health plan is considered creditable coverage under Medicare rules.

If you are unsure whether you have a valid reason to delay Part B enrollment, contact State Health Insurance information Program (SHIP), which offers free counseling. You can find your state's SHIP by calling 1-800-MEDICARE or visiting Medicare.gov. A counselor can review your specific situation and tell you whether a penalty would explore.

When you are ready to enroll, you can do it online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

Frequently Asked Questions

Can I enroll in Part B after I turn 65 if I did not sign up before?

Yes, but you may face a penalty. You can enroll during the General Enrollment Period (January 1 to March 31 each year), but your premium will increase by 10 percent for each year you delayed. If you have a valid reason for the delay — such as employer coverage or a may have access to life event — you may enroll without penalty within a set timeframe.

Do I have to take Part B if I have employer coverage?

Not if your employer has 20 or more employees. You can stay on your employer plan and delay Part B without penalty. When you leave that job, you have eight months to enroll in Part B. If your employer has fewer than 20 employees, you should enroll in Part B at 65.

What is the difference between Part B and Part D?

Part B covers doctor visits, lab work, and outpatient care. Part D covers prescription drugs. You need both if you take medications regularly. Part D is optional, but if you delay enrolling when first may be able to access, you may face a penalty.

How much does Part B cost in 2024?

The standard premium is $164.90 per month in 2024, but it increases each year. If your income is above certain thresholds, you pay more. Premiums are deducted from your Social Security check automatically.

Can I switch from Original Medicare to Medicare Advantage later?

Yes. You can switch during the Annual Enrollment Period (October 15 to December 7) each year, or during the Medicare Advantage Open Enrollment Period (January 1 to March 31). If you switch back to Original Medicare from Advantage, you have a limited window to enroll in Medigap without medical underwriting.