Understanding Medicare Part B

Medicare Medical Insurance Benefits

Medicare has four parts, or programs, that provide coverage for different health-related services. Together, Medicare Parts A and B are called Original (or Traditional) Medicare. Part C is Medicare Advantage (which combines the benefits of Parts A, B, and usually D, into one plan), and Part D is prescription drug coverage. Parts C and D are offered by private insurance companies.

This article will explain what you need to know about Medicare Part B, also known as the Medical Insurance program. Part B coverage helps pay for medically necessary outpatient and physician services, such as:

  • Physician services (including physician services that are provided while you're hospitalized)
  • Outpatient care, including services such as stitches or outpatient surgery
  • Some home health services, such as physical and occupational therapy
  • Some preventive services, including certain vaccines
  • X-rays and diagnostic testing
  • Dialysis
Female doctor talking to mature female patient

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Who's Eligible for Part B?

Most Medicare enrollees don't have to pay a premium for Part A because they (or their spouse) have worked at least 10 years in a job where they paid Medicare taxes. If you're eligible for premium-free Medicare Part A, you're also eligible for Medicare Part B.

Some people are eligible for Medicare Part A but have to pay a premium for it because they don't have enough work history (their own, or their spouse's) to receive it for free; those people can also enroll in Part B.

If you're turning 65 and already receiving benefits from Social Security or the Railroad Retirement Board, you'll be automatically enrolled in Medicare Part A and Part B.

You should receive your Medicare cards in the mail about three months before you turn 65. At that point, you'll have the option to decline Part B coverage if you want to.

Delaying Enrollment

Part B has a monthly premium for everyone, so if you or your spouse still have employer-sponsored coverage, you can opt to delay your enrollment in Part B and sign up for it later on, once you no longer have the employer-sponsored plan.

If you delay enrollment in Part B and you don't have coverage under a current employer's plan, you'll have to pay a late enrollment penalty once you do eventually enroll in Part B.

Also, if you miss your initial enrollment period and don't have a special enrollment period (due to retirement, for example, and the end of your employer-sponsored coverage) you can only enroll during the general enrollment period that runs from January through March each year, with coverage effective the month after you enroll. In that case, so you could have a gap in coverage and potentially be charged a late enrollment penalty for as long as you have Part B coverage.

If you're turning 65 and not yet receiving benefits from Social Security or the Railroad Retirement Board, you'll have a seven-month window during which you can enroll in Medicare (three months before you turn 65, the month you turn 65, and the three following months).

During this window, you can enroll in Part B or you can opt to delay it, as described above, with the same caveats about the late enrollment penalty.

If you're enrolling in Medicare Part A but with a premium—because your work history isn't sufficient to allow you access to premium-free Medicare Part A—you're eligible for Medicare Part B as well. Your premium for Part B will be the same as the premium everyone else pays (note that people with high incomes pay higher premiums for Part B).

If you're eligible for Medicare prior to age 65, you're eligible for Medicare Part B as well as Part A. For people under age 65, three different scenarios can trigger Medicare eligibility:

  • You've been receiving Social Security Disability Insurance or Railroad Retirement Board disability benefits for 24 months. You'll automatically be enrolled in Medicare as of the 25th month of disability.
  • You have permanent kidney failure requiring ongoing dialysis or a kidney transplant. Your Medicare coverage begins the first day of your fourth month of dialysis, or the first month of dialysis if you're participating in a home dialysis program.
  • You've been diagnosed with amyotrophic lateral sclerosis (ALS). You get Part A the month your disability benefits begin. There used to be a five-month waiting period before a person with ALS could begin receiving Social Security disability benefits, but legislation enacted in late 2020 eliminated that waiting period.

Paying a Premium for Part B

You'll need to pay a monthly premium for Part B that will be deducted from your monthly Social Security check—or paid directly to Medicare if you're not receiving a Social Security check.

Most people pay a standard monthly premium for Part B, which is $164.90 in 2023. Your premiums will be higher if you make more than $97,000 a year (this is always based on the income you earned two years earlier, so if your 2021 income, as a single individual, was more than $97,000, you can expect a higher Part B premium in 2023).

Although the Part B premium tends to increase over time—it was just $4 a month in 1970—there have been some years when the premium has declined or stayed the same.

You can decline Medicare Part B in order to avoid paying the monthly premium. If you're automatically enrolled, instructions for opting out will be included with your Medicare card. If you're enrolling during your initial enrollment period, you'll be able to enroll in Part A on its own.

Before you opt out of Part B, make sure you fully understand how the Part B late enrollment penalty works, and understand that your opportunity to enroll later on will be limited to the general enrollment period that runs from January through March.

Neither of these restrictions applies, though, if you're delaying Part B because you have coverage from your current employer or your spouse's current employer.

If your income is limited and you cannot afford the monthly premium Part B, your state may have a program to help. These resources can help you find out what's available:

What Does Part B Cover and What Will I Pay?

Medicare Part B has an annual deductible of $226 in 2023.

You must pay all Medicare-approved Part B costs until you meet the deductible before Medicare starts to pay its share (note that some preventive care, such as certain vaccines, are covered by Part B without the enrollee having to pay the deductible).

After you meet your deductible, you'll generally be responsible for coinsurance of 20% of the Medicare-approved amount for the service. As described below, you can purchase a Medigap plan (Medicare Supplement insurance) that will cover some or most of these charges.

In general, Medicare Part B covers two types of services:

  • Medical services: Healthcare services (and related supplies) that you may need to diagnose and treat a medical condition. These services are often provided on an outpatient basis, but can also be provided during an inpatient stay. Medicare will only pay for services that they define as being medically necessary.
  • Preventive services: Healthcare services to prevent illness (such as a flu shot) or help detect an illness in an early stage so it can be managed before getting worse (such as screening for colon cancer).

Medical Services

Some examples of medical services that are covered by Part B include:

  • Ambulance services: Only if necessary and only to the nearest appropriate medical facility
  • Clinical laboratory services: Certain blood tests, urine tests, and some screening tests
  • Diabetes supplies: Blood sugar monitors, test strips, and lancets
  • Dialysis: Ongoing treatment for a person with kidney failure
  • Practitioner services: Care and prevention services in the office and some services in the hospital
  • Durable medical equipment: Things your healthcare provider orders for use in the home, such as oxygen equipment, wheelchairs, walkers, and hospital beds
  • Emergency room services: Treatment of a serious injury or sudden illness
  • Mental health care: Diagnosis and treatment of mental health conditions such as depression, anxiety, or substance abuse
  • Occupational therapy, physical therapy, and speech-pathology services: To help you return to normal function after an illness or injury
  • Hospital outpatient services: Includes healthcare provider's services in a hospital outpatient department plus things like X-rays, EKGs, scans, a cast, or wound management
  • Limited prescription drug coverage: Generally limited to injections in the healthcare provider's office, certain oral cancer drugs, and some drugs used with equipment like a nebulizer or infusion pump

Coverage for most other prescription drugs is provided under Medicare Part D, which is a separate program offered by private insurance companies.

Preventive Services

Some examples of covered preventive services include:

  • Abdominal aortic aneurysm screening: A one-time screening for people at risk
  • Bone density test: Osteoporosis screening to gauge fracture risk
  • Cancer screening: Tests to help detect colorectal, breast, cervical, and prostate cancers
  • Diabetes screening: For people at risk for diabetes
  • Glaucoma tests: For people at high risk for glaucoma, a serious eye disease
  • Heart disease screening: To help determine your risk of a heart attack
  • Vaccinations: Flu, COVID, hepatitis B, and pneumococcal vaccines (there is no cost for these vaccines)
  • Smoking cessation: Counseling to help you stop smoking
  • "Welcome to Medicare" visit: A comprehensive checkup during the first 12 months you're enrolled

Note: The above lists are only a partial outline of services covered under Medicare Part B. For a full list, plus annual deductible and coinsurance information, see the annual "Medicare and You" handbook.

Should I Enroll in Medigap?

While Medicare Part B will most likely pay for most of your outpatient medical expenses, you'll have to pay the deductible and coinsurance when you receive services that are covered under Part B, resulting in some out-of-pocket costs.

There is no cap on how high those costs can be. Commercial insurance plans have caps on out-of-pocket costs, but Original Medicare does not.

Many Medicare beneficiaries have supplemental coverage from an employer or retiree plan, or from Medicaid. If you don't have access to one of these, you'll want to consider purchasing a Medigap plan to help pay these out-of-pocket costs. A Medigap plan will pay some or all of the deductible and coinsurance charges that go along with Medicare Part A and Part B, for services that are covered under Original Medicare.

If you became eligible for Medicare on or after January 1, 2020, you can't purchase Medigap plans that cover the Part B deductible. But it's still possible to purchase a Medigap plan that will cover all of the rest of your out-of-pocket charges for Part A and Part B (note that Medigap plans won't cover out-of-pocket costs for services that aren't covered under Original Medicare, such as dental care).

If you enroll in a Medicare Advantage plan, your out-of-pocket costs will be capped (except for prescription drug costs). Medigap plans cannot be used in conjunction with Medicare Advantage.


Medicare Part B is the portion of Original Medicare that covers outpatient and physician services. It has an annual deductible ($226 in 2023) and then covers 80% of the Medicare-approved amount for covered services. The enrollee pays the other 20% unless they have supplemental coverage that picks up this cost.

A Medicare-eligible person can enroll in Medicare Part A (which has no premium for most people) and delay Part B, which does have a monthly premium. But this is generally only recommended if you have coverage from a current employer (your own, or your spouse's).

A Word From Verywell

If you're considering going without Medicare Part B because of the monthly premium cost, make sure that you fully understand the ins and outs of this. You can talk with a SHIP counselor in your area, or call 1-800-MEDICARE to get your questions answered. If you delay Part B without having coverage from a current employer, you could face late enrollment penalties if you sign up for Part B later on, and you'll also be limited in terms of when you can sign up for it.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Centers for Medicare & Medicaid Services. Outpatient Medical and Surgical Services and Supplies.

  2. U.S. Centers for Medicare & Medicaid Services. Medicare costs at a glance.

  3. U.S. Centers for Medicare & Medicaid Services. Enrolling in Medicare Part A & Part B.

  4. U.S. Centers for Medicare & Medicaid Services. Getting Medicare if you have a disability.

  5. U.S. Centers for Medicare & Medicaid Services. Signing up for Medicare if you have ESRD.

  6. Norris, Louise. medicareresources.org. Medicare eligibility for ALS and ESRD patients.

  7. U.S. Centers for Medicare & Medicaid Services. Part B costs.

  8. Medicare Board of Trustees. 2019 Annual Report of the Board of Trustees of the Federal Hospital Insurance and Federal Supplementary Medical Insurance Trust Funds.

  9. U.S. Centers for Medicare & Medicaid Services. What Part B covers.

  10. U.S. Centers for Medicare & Medicaid Services. Preventive & screening services.

  11. Kaiser Family Foundation. Sources of supplemental coverage among Medicare beneficiaries in 2016.

  12. U.S. Centers for Medicare & Medicaid Services. Choosing a Medigap policy: A guide to health insurance for people with Medicare.

By Michael Bihari, MD
Michael Bihari, MD, is a board-certified pediatrician, health educator, and medical writer, and president emeritus of the Community Health Center of Cape Cod.