What Medicare Part B covers and who must have it

Medicare Part B covers doctor visits, outpatient care, lab tests, X-rays, and some preventive services. It is not automatic — you have to sign up for it, and most people pay a monthly premium. If you are already on Medicare Part A (hospital insurance), you will likely need Part B unless you are still working and covered by an employer health plan.

Part B becomes your responsibility to enroll in during your initial enrollment period, which starts three months before the month you turn 65. If you miss this window and do not have other coverage, you will pay a permanent penalty on your Part B premium for as long as you have Medicare. The penalty is 10 percent for each full year you were may be able to access but did not enroll.

The main exception is if you are covered by a current employer health plan (yours or your spouse's) and you are still working. In that case, you can delay Part B without penalty as long as that coverage continues. You will need to show proof of that employer coverage when you do enroll.

Key Takeaways

  • Part B covers doctor visits, outpatient procedures, lab work, and preventive care that Part A does not include.
  • You must enroll during your initial enrollment period (three months before to three months after the month you turn 65) or face a permanent 10 percent premium increase.
  • If you have health coverage through a current employer, you can delay Part B enrollment without penalty as long as that coverage lasts.
  • Part B has a monthly premium (the amount changes yearly), an annual deductible, and coinsurance costs for most services.
  • You can change your Part B coverage during the annual enrollment period (October 15 to December 7) if you want to switch to a Medicare Advantage plan or Medigap policy.

What Part B costs and what you pay out of pocket

The standard Part B premium in 2024 is $164.90 per month for most people, though higher earners pay more. This amount is deducted from your Social Security check if you receive benefits, or you pay it directly to Medicare. The premium changes each year, usually increasing slightly.

Beyond the premium, you also pay an annual deductible (currently $240) before Medicare starts to pay its share. After you meet the deductible, you typically pay 20 percent of the cost for most services, and Medicare pays 80 percent. For some preventive services — like annual wellness visits, cancer screenings, and vaccinations — you pay nothing if you see an in-network provider.

These out-of-pocket costs can add up if you have frequent doctor visits or need specialist care. Many people buy a Medigap policy (supplemental insurance) to cover the 20 percent coinsurance, or they choose a Medicare Advantage plan instead of Original Medicare, which may have different cost structures and provider networks.

When you can enroll or change your Part B coverage

Your initial enrollment period is seven months long: 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 on the first day of the month you turn 65 (or the first day of the month after you enroll, whichever is later).

If you miss your initial enrollment period and do not have may have access to coverage through an employer, you can enroll during the general enrollment period from January 1 to March 31 each year. Coverage starts July 1 if you enroll during this time. However, you will owe the permanent penalty on top of your regular premium.

Once you are enrolled in Part B, you can switch to a Medicare Advantage plan or back to Original Medicare during the annual enrollment period from October 15 to December 7. Changes take effect January 1. If you want to add or change a Medigap policy, the rules are different — you have a six-month window starting the month you turn 65 and enroll in Part B, during which insurers cannot deny you or charge more based on health conditions.

Part B versus Medicare Advantage: which path makes sense

With Original Medicare Part B, you can see any doctor or specialist who accepts Medicare, and there are no referrals required. You have more flexibility in choosing providers, but you are responsible for the 20 percent coinsurance on most services. Many people pair Part B with a Medigap policy to cover those costs.

Medicare Advantage plans (Part C) are an alternative to Original Medicare. They bundle Part A, Part B, and usually prescription drug coverage into one plan run by a private insurance company. Advantage plans often have lower or zero premiums, but they typically require you to use in-network doctors and may require referrals to see specialists. Out-of-pocket costs vary by plan and can include copays instead of coinsurance.

The choice depends on your priorities. If you want maximum flexibility and do not mind paying for supplemental coverage, Original Medicare with Part B and a Medigap policy may suit you. If you prefer predictable costs and do not mind a narrower network, an Advantage plan might be better. You can switch between these options each year during the annual enrollment period.

What happens if you do not enroll in Part B

If you do not enroll in Part B when you are first may be able to access and you do not have other may have access to coverage, you will face a permanent premium penalty. That 10 percent increase applies to every month you have Part B going forward — it does not go away after a few years.

Without Part B, you will have only Part A coverage, which pays for hospital stays, skilled nursing care, and some home health services. You will be responsible for the full cost of doctor visits, lab work, X-rays, and outpatient procedures. This can become very expensive quickly if you need ongoing medical care.

If you realize you missed your enrollment window, you may have a second chance during the general enrollment period (January 1 to March 31), though coverage would not start until July 1 and the penalty would explore. Some people may have access to for a special enrollment period if they had a may have access to life event, such as losing employer coverage — contact Medicare directly to ask if you may have access to.

How to sign up for Part B

You can enroll in Part B online through 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 information about any current health coverage you have.

If you are already receiving Social Security benefits, Medicare will contact you automatically about three months before you turn 65. You can enroll through the notice they send, or you can enroll on your own through any of the methods above. If you are not yet receiving Social Security, you will need to contact Medicare or Social Security to enroll.

Have your current insurance information ready, especially if you have employer coverage or are on Medicaid. You may also want to know whether you plan to choose Original Medicare with a Medigap policy or switch to a Medicare Advantage plan, since that affects which forms you need to submit.

Questions to ask your doctor or Medicare

Before you enroll, ask your current doctor whether they accept Medicare and what your out-of-pocket costs would be under Part B. If you are considering a Medicare Advantage plan, ask whether your doctor is in that plan's network and whether you would need referrals for specialist care.

Contact Medicare at 1-800-MEDICARE to ask about your specific enrollment important date, whether you may have access to for a special enrollment period if you missed your initial window, and what the current Part B premium and deductible are. You can also ask whether you are may be able to access for Extra Help (a program that covers Part B premiums and cost-sharing for people with limited income) or Medicaid (which can cover Part B costs in some states).

Frequently Asked Questions

What if I am still working at 65 — do I have to enroll in Part B?

No, if you are covered by your employer's health plan and you are still actively working, you can delay Part B without penalty. When you do enroll (after you leave your job or lose that coverage), you will have a special enrollment period to sign up without the permanent penalty. You will need to provide proof of your employer coverage.

Can I drop Part B after I enroll?

Yes, but only during the annual enrollment period (October 15 to December 7). If you drop Part B and later want it back, you will owe the permanent penalty unless you have a may have access to reason, such as gaining employer coverage. It is usually better to keep Part B enrolled even if you do not use it much, to avoid the penalty.

Does Part B cover prescription drugs?

No, Part B does not cover prescription medications. You need Part D (prescription drug coverage) for that. Part D is sold by private insurers and you enroll separately. If you do not enroll in Part D when you first become may be able to access, you may owe a penalty if you enroll later.

What is the difference between Part B and a Medigap policy?

Part B is the government insurance that covers 80 percent of most services after you meet the deductible. A Medigap policy is supplemental insurance sold by private companies that covers some or all of the 20 percent coinsurance you would otherwise pay. You can have both at the same time.

If I have Medicare Advantage, do I still need Part B?

Medicare Advantage includes Part B coverage as part of the plan, so you do not buy Part B separately. However, you must be enrolled in Part A and Part B to join an Advantage plan. You cannot have both Original Medicare Part B and a Medicare Advantage plan at the same time.