Medicare Part B does not cover most prescription drugs — that is a separate benefit called Part D
Medicare Part B covers doctor visits, hospital outpatient care, medical equipment, and some preventive services. It does not pay for prescription medications you pick up at a pharmacy. If you need prescription coverage, you must enroll in Part D, which is the prescription drug plan, or choose a Medicare Advantage plan (Part C) that includes drug coverage built in.
The one exception: Part B does cover certain drugs that are injected or infused in a doctor's office or hospital outpatient setting — such as chemotherapy, some biologics for rheumatoid arthritis, or certain vaccines. If your doctor administers the drug to you during a visit, Part B may cover it. If you take it at home, Part D covers it instead.
Key Takeaways
- Part B covers drugs given to you by a doctor or nurse in a medical setting, but not drugs you take at home.
- Part D is the separate prescription drug plan that covers medications you pick up at a pharmacy or take at home.
- Medicare Advantage plans (Part C) often include prescription drug coverage, so you do not need to enroll in Part D separately.
- You can enroll in Part D during your initial enrollment period or during the annual open enrollment period in the fall.
- If you do not enroll in Part D when you first become may be able to access, you may pay a penalty for each month you delay.
When Part B covers drugs in a medical setting
Part B will pay for drugs that a doctor or other healthcare provider gives you during an office visit or in a hospital outpatient department. This includes chemotherapy drugs, immunosuppressants after an organ transplant, some biologics for autoimmune conditions, and certain vaccines (like the pneumococcal vaccine or RSV vaccine for older adults).
You pay your Part B coinsurance — usually 20 percent of the cost after you meet your deductible — for these drugs. The provider's office or hospital bills Medicare directly, so you do not pay upfront and then wait for reimbursement.
If your doctor prescribes a drug that you will take at home, even if it is the same medication you received in the office, Part D covers it instead. For example, if you receive an infusion of a biologic at the hospital and then take a related oral medication at home, Part B covers the infusion and Part D covers the pill.
Part D prescription drug coverage and how to enroll
Part D is a separate monthly insurance plan run by private insurers under contract with Medicare. It covers medications you take at home — pills, inhalers, injections you give yourself, and liquids. Each Part D plan has its own list of covered drugs, called a formulary, and its own cost-sharing structure.
You can enroll in Part D when you first become may be able to access for Medicare (usually at age 65) or during the annual open enrollment period, which runs from October 15 to December 7 each year. Coverage begins the first day of the month after you enroll. If you miss your initial enrollment window and do not have other creditable prescription coverage, you will owe a late enrollment penalty — a percentage added to your Part D premium for as long as you have the plan.
To find and compare Part D plans in your area, you can use the Medicare Plan Finder tool on Medicare.gov. You will need your zip code and a list of your current medications to see which plans cover them and what your out-of-pocket costs would be.
Medicare Advantage plans and built-in drug coverage
If you choose a Medicare Advantage plan (Part C) instead of Original Medicare, most of these plans include prescription drug coverage. You do not enroll in Part D separately; the drug benefit is part of your Advantage plan. You pay the plan's copay or coinsurance for each prescription, and the plan's formulary determines which drugs are covered.
Medicare Advantage plans vary widely in their drug coverage, so compare the formularies and costs of plans available in your area during open enrollment. Some plans may not cover a drug you need, or may require prior authorization from your doctor before they will pay for it.
How Part D costs work
Part D plans have a monthly premium, an annual deductible (which varies by plan), and cost-sharing for each prescription. Cost-sharing typically includes a copay (a flat dollar amount per prescription) or coinsurance (a percentage of the drug's cost). Some plans have a $0 deductible.
Once your total out-of-pocket spending reaches a certain amount (called the out-of-pocket threshold, which changes each year), you enter the "catastrophic coverage" phase. At that point, you pay a small copay or coinsurance, and Medicare and your plan split the remaining cost. This protects you from extremely high drug bills.
If your income is low, you may may have access to for Extra Help, a federal program that pays some or all of your Part D premiums and cost-sharing. You can explore through your local Social Security office or online at SSA.gov.
What happens if you do not enroll in Part D
If you have Original Medicare and do not enroll in Part D when you first become may be able to access, you will pay the full cost of any prescription drugs out of your own pocket. There is no Medicare coverage to fall back on.
If you later decide to enroll, you will owe a late enrollment penalty. The penalty is calculated as 1 percent of the national average Part D premium for each full month you were not enrolled and did not have other creditable coverage. This penalty is added to your monthly premium and stays with you for as long as you have Part D.
The only exception is if you had other creditable prescription coverage — such as coverage through a current or former employer, a union, TRICARE, or the Veterans Health Administration — during the time you were not enrolled in Part D. If you did, you can enroll without a penalty.
Drugs that Part B covers in a doctor's office versus Part D at home
| Type of Drug | Given in Doctor's Office or Hospital | Taken at Home |
|---|---|---|
| Chemotherapy | Part B covers | Part D covers |
| Biologic for rheumatoid arthritis | Part B covers if infused | Part D covers if injected or taken orally at home |
| Immunosuppressant after transplant | Part B covers if given in office | Part D covers if taken at home |
| Vaccines (pneumococcal, RSV, flu) | Part B covers | Not typically prescribed for home use |
| Insulin | Part B covers if given in office | Part D covers if you inject at home |
Frequently Asked Questions
Does Part B cover insulin?
Part B covers insulin only if a doctor or nurse injects it for you during an office or hospital visit. If you inject insulin yourself at home, Part D covers it. Part B also covers insulin pumps and related supplies as durable medical equipment.
What if my Part D plan stops covering a drug I take?
Plans can change their formularies each year. If your plan removes a drug you need, you can switch to a different Part D plan during the annual open enrollment period (October 15 to December 7). You can also ask your doctor to request a coverage exception from your current plan, though approval is not may provide.
Can I use Part B coverage and Part D at the same time?
Yes. Part B covers drugs administered in a medical setting, and Part D covers drugs you take at home. They work together, not against each other. If you receive a drug in your doctor's office, Part B pays. If you fill a prescription at a pharmacy, Part D pays.
Do I have to enroll in Part D if I am still working and have employer coverage?
No, as long as your employer plan is creditable coverage — meaning it covers prescription drugs at least as well as Part D does. When you retire and lose that coverage, you can enroll in Part D without a late penalty, as long as you sign up within 63 days of losing your employer coverage.
What is the difference between a Part D plan and a Medicare Advantage plan with drug coverage?
Part D is a standalone prescription drug plan you add to Original Medicare. A Medicare Advantage plan is a complete alternative to Original Medicare and includes drug coverage built in. With Advantage, you get medical and drug coverage from one plan. With Original Medicare plus Part D, you have separate coverage for medical care and prescriptions.