Which part of Medicare pays for your medicines?
Two people with the same cancer can face completely different bills depending on whether their treatment goes in through a drip or comes home in a bottle. It is the most consequential piece of Medicare arithmetic there is, and almost nobody is told about it at diagnosis.
Given to you at a clinic → usually Part B
Infusions and injections a nurse or doctor administers. You generally pay 20% of the approved amount — and under Original Medicare alone, nothing caps that 20%.
Collected from a pharmacy → usually Part D
Pills and anything you take yourself. There is a deductible and tiers — but there is also a hard annual cap, after which covered drugs cost you nothing.
“Usually” is doing real work in those two sentences. There are exceptions — some drugs you take at home are still billed under Part B, and a drug can move between them depending on the setting it is given in. If a medicine matters to your budget, ask your oncology practice’s billing team which part they bill it under. They will know.
Your medication list
Add each medicine, say how you take it, and the worksheet will tell you which part of Medicare usually pays. Then check each one against the plan’s drug list. Saved on this device only — nothing is sent anywhere.
Usually covered under: Needs checking
Usually covered under: Needs checking
If it is Part B
You generally pay 20% of the Medicare-approved amount after the Part B deductible, and under Original Medicare on its own there is no annual ceiling on that 20%. On infusions billed in the thousands, that adds up fast. A Medigap policy or a Medicare Advantage plan’s out-of-pocket maximum is what caps it.
If it is Part D
Your plan may charge a deductible of up to $615, then a copay or percentage by tier — but once you have paid $2,100 out of pocket in 2026, you pay nothing more for covered drugs for the rest of the year. If that lands as one enormous January bill, ask your plan about the Medicare Prescription Payment Plan, which spreads it into monthly instalments.
If the plan says no
A drug missing from the list is not the end of the conversation. Three things are worth asking for by name, because plans do not volunteer them:
- A formulary exception
- Covers a drug that is not on the list, when your prescriber explains why the alternatives will not work for you. Also the route to waive step therapy or a quantity limit.
- A tiering exception
- Moves a covered drug to a cheaper tier. Worth thousands a year on a specialty-tier cancer drug.
- An expedited decision
- 24 hours instead of 72, whenever waiting could seriously harm your health. Your oncologist saying so is what triggers it.
The clock on an exception does not start until your prescriber’s supporting statement reaches the plan, so the single most useful thing you can do is ring the practice and ask them to send it today.
How to appeal a drug denialTalk it through with a Medicare counselor
Every state has a State Health Insurance Assistance Program — trained counselors who sit down with you one-on-one, go through your own medications and doctors, and help you work out what your options actually cost. It is free, it is confidential, and they earn nothing whichever plan you choose. If you only do one thing on this page, do this one.