Medicare Part B covers outpatient costs related to diagnosing and treating medical conditions. Medicare Part D covers prescription drugs. Specific rules usually apply to both.
Medicare is the federal government’s health insurance coverage for people who are ages 65 years and over or who have specific medical conditions. Medicare packages have different parts that cover various aspects of medical care. Parts B and D are examples of this coverage.
This article will explain the differences between Medicare Part B and Part D, including those relating to costs and coverage.
Glossary of Medicare terms
- Out-of-pocket cost: This is the amount a person must pay for care when Medicare does not pay the total amount or offer coverage. Costs can include deductibles, coinsurance, copayments, and premiums.
- Premium: This is the amount of money someone pays each month for Medicare coverage.
- Deductible: This is an annual amount a person must spend out of pocket within a certain period before Medicare starts to fund their treatments.
- Coinsurance: This is the percentage of treatment costs that a person must self-fund. For Medicare Part B, coinsurance is 20%.
- Copayment: This is a fixed dollar amount a person with insurance pays when receiving certain treatments. For Medicare, this usually applies to prescription drugs.
Medicare has four parts — A, B, C, and D.
- Part A: This part covers inpatient care, hospice care, some home health and rehabilitation costs, and skilled nursing services. Part A is one part of Original Medicare. Some people are eligible for free Part A coverage.
- Part B: This portion of Medicare covers outpatient medical services, such as doctor’s visits, durable medical equipment, and select prescription medications. Part B is another part of Original Medicare, meaning a person will pay the premium to the federal government.
- Part C: Private insurers offer Part C plans, also called Medicare Advantage plans. A Medicare Advantage plan must cover everything Original Medicare covers, and it usually offers additional services.
- Part D: This part of Medicare covers prescription drugs and may sometimes be called a prescription drug plan, or PDP. The federal government requires that all people ages 65 years and over have basic prescription drug coverage, which typically means coverage for the most commonly prescribed medications. Private companies administer Part D plans.
Medicare Part B covers most outpatient doctor’s visits and services people receive in a doctor’s office. It also includes coverage for durable medical equipment, such as wheelchairs, crutches, or other assistive devices.
Part B may also cover some medications that Part D does not cover, such as:
- antigens that a doctor typically prepares
- blood clotting factors
- injectable or infused drugs
- erythropoiesis-stimulating agents, which doctors commonly use to treat end stage renal disease (ESRD)
- immunosuppressive drugs
- injectable medications for osteoporosis
- intravenous (IV) immunoglobulin at home
- oral medications for ESRD
- parental and enteral nutrition for IV and tube feeding
- vaccinations
- monoclonal antibodies for the treatment of early Alzheimer’s Disease
- preexposure prophylaxis (PrEP), or HIV prevention drugs
Part B may cover other drugs as well. A person can check their benefits for information about a specific medication.
Medicare Part D offers a wide range of benefits relating solely to prescription drugs.
The plans must provide a medication list, called a formulary. A formulary must cover at least two drugs in each commonly prescribed category. Examples of these categories include blood pressure and diabetes medications.
Formularies usually have tiers, or levels. Lower tiers typically contain less costly generic medications, while higher tiers contain more expensive brand-name medications.
Part B and Part D are essential in protecting the health of older adults and those with some disabilities. Medicare negotiates approved medical costs to help prevent medical providers from unfairly pricing services.
Coverage: Part B vs. Part D
There are differences in the coverage that each of Medicare’s four plans provides. The table below shows the differences between Part B and Part D:
| Comprehensive medical services | Limited coverage | Choice of providers | Low cost pricing | Deductibles | Plan options | |
|---|---|---|---|---|---|---|
| Part B | yes | yes | yes | no | yes | no |
| Part D | no | no | no | yes | yes | yes |
Costs: Part B vs. Part D
The costs for Part B and Part D vary depending on the plan and options.
Part B
A person must pay a monthly premium for Medicare Part B. The premiums usually change each year. For 2025, the standard premium is $185.
In addition, Part B has a 2025 deductible of $257.
A 20% coinsurance for most Medicare-approved services will apply after a person has paid their deductible. The coinsurance applies to specific services, including doctor’s visits and some prescription drugs.
Part D
As private insurers administer Part D plans, the costs can vary by plan and location.
People can choose a stand-alone Part D plan, also called a prescription drug plan, or they can choose to include drug coverage in a Medicare Advantage package.
Stand-alone drug plan premiums are estimated to be around six times higher than drug benefits included in Medicare Advantage plans, according to the nonprofit KFF.
In 2025, the average prescription drug plan monthly premium is estimated to be around $45, the KFF reports.
Medicare Advantage and Part D
When people choose to add drug coverage through Medicare Advantage, premiums may start from as little as $7 per month, per the KFF.
Eligibility and enrollment: Part B vs. Part D
Not everyone who turns 65 years old must enroll in Medicare. Some people may continue to work and choose to use their employer’s or spouse’s health insurance.
In these instances, a person must send documentation to the Centers for Medicare & Medicaid Services (CMS) to show that they have appropriate medical insurance coverage.
If a person becomes ineligible for an alternative health insurance plan outside of the Medicare annual enrollment period, they may qualify for a special enrollment period during which they can still enroll for Medicare coverage.
Alongside Part A, a person should enroll in Medicare parts B and D when they first become eligible. Waiting until after the initial enrollment period (IEP) could result in premium penalties. The IEP ends 3 months after the month in which a person turns 65 years old.
Unlike some private insurance plans, Medicare accepts all individuals who qualify without considering preexisting health conditions.
Extra Help
A person who meets the Medicare low income criteria may qualify for Extra Help. The Extra Help program provides financial support to people who need assistance paying for prescription drugs.
Medicare resources
For more resources to help guide you through the complex world of medical insurance, visit our Medicare hub.
Part B and Part D are two Medicare parts that help beneficiaries pay their healthcare costs.
Medicare Part B pays for eligible outpatient doctor’s visits, some medical procedures, and specific prescription drugs.
However, it is Medicare Part D that pays for most take-home medications.
People can choose a stand-alone Part D plan, also called a prescription drug plan, or include drug coverage within a Medicare Advantage package.
