The Drug Your Doctor Gives You Is Not on Your Drug Plan

1. The question nobody asks at the counter

Somebody came into the office last October with a tidy list of eight medications and a question about which drug plan to choose. Seven of the eight were tablets. The eighth was an infusion he received every four weeks at a clinic in Fort Lauderdale, and it was the one that accounted for almost all of what he spent on healthcare in a year. He had spent two hours comparing drug plans on a drug that no drug plan was paying for.

Medicare’s own rule of thumb is one line long and it is worth memorising: Part B generally covers drugs you would not typically give to yourself. Something a clinician administers is usually Part B. Something you collect and take at home is usually Part D. That sounds like an administrative distinction. It is actually the difference between a copay and an open-ended 20 percent.¹

2. What Part B pays for

Part B is the medical half of Original Medicare, and it pays for drugs that arrive as part of treatment rather than as a prescription you fill. The categories Medicare lists are:¹

• Injectable and infused drugs given by a licensed provider — in a doctor’s office, an infusion centre or a hospital outpatient department. This is the biggest category and the one that catches most people.
• Drugs infused through equipment Medicare covers as durable medical equipment, such as an infusion pump.
• Transplant immunosuppressive drugs, where Medicare helped pay for the transplant itself.
• Some oral cancer drugs — specifically where the same drug is available in injectable form, or is a prodrug of the injectable version.
• Certain dialysis drugs, including calcimimetics and phosphate binders for end-stage renal disease.
• Flu, pneumococcal, COVID-19 and hepatitis B vaccines.

Notice what these have in common. None of them is something you pick up at a pharmacy counter and swallow at home. If your treatment involves sitting in a chair while somebody administers it, the odds are strongly that you are in Part B territory, whatever your drug plan’s formulary says.

3. What Part D pays for

Part D is the drug coverage you buy separately or get bundled inside a Medicare Advantage plan, and Medicare’s description of the relationship is that it covers many drugs Part B does not. In practice that means nearly everything you collect at a pharmacy and take yourself: tablets, capsules, most self-administered injectables, inhalers, creams and the rest.¹

This is the half your formulary describes, the half with tiers and prior authorisation and preferred pharmacies, and the half the $2,400 out-of-pocket maximum was written for. It is also the half that a Plan Compare search prices for you. All of which is useful — and all of which is silent about the infusion.³

4. Insulin, which sits on both sides

Insulin is the clearest example of the same drug landing on either side depending on how it reaches you. Part B covers insulin used with an insulin pump that Medicare covers as durable medical equipment. It does not cover insulin you self-administer with a pen, or with a disposable patch pump — those are Part D, along with inhaled insulin.²

The good news is that for insulin the split matters much less than usual, because the cost was levelled across both parts. A one-month supply of each covered insulin product costs no more than $35, and no deductible applies, whether it comes through Part B or Part D. A three-month supply is no more than $35 for each month’s supply. If you are being charged more than that for covered insulin, something is wrong and it is worth a phone call rather than a shrug.²

5. Vaccines, which are also split

Vaccines are split the same way, and this one costs people money every autumn. Part B covers the flu, pneumococcal, COVID-19 and hepatitis B vaccines, and you pay nothing for them when the provider accepts assignment — the Part B deductible does not apply.¹

Everything else for adults runs through Part D: shingles, RSV, Tdap and the rest. Those recommended by the Advisory Committee on Immunization Practices carry no copay and no deductible under Part D. The practical consequence is that a shingles vaccine should cost you nothing, and if a pharmacy quotes you a price for one, the problem is usually billing rather than coverage.⁷

6. Why it changes what you owe

Here is why the filing question turns into a money question. The two parts price drugs in completely different ways, and one of them has no ceiling at all.⁴

	A Part B drug	A Part D drug
What you pay	Up to 20% of the Medicare-approved amount	A copay or coinsurance set by your plan
Deductible	The Part B deductible — $283 in 2026	The plan’s drug deductible, up to $700 in 2027
Annual out-of-pocket ceiling	None under Original Medicare	$2,400 in 2027
Where you get it	Administered by a provider	Collected at a pharmacy
Shown on a plan formulary	No	Yes
Priced by Plan Compare	No	Yes

The row to sit with is the third one. Under Original Medicare on its own, there is no yearly limit on what you pay out of pocket — that is Medicare’s own phrasing, and it applies to Part B drugs as much as to any other Part B service. Twenty percent of a $6,000 infusion is $1,200. Thirteen of those in a year is $15,600, and nothing in Original Medicare stops the meter.⁵

7. The $2,400 cap, and what it is written against

The $2,400 figure has done a great deal of good and it has also created a false sense of safety. Read Medicare’s wording closely: you pay coinsurance until your out-of-pocket spending on covered Part D drugs reaches $2,400 in 2027. Covered Part D drugs. That is the boundary of the sentence.³

Spending on a drug paid under Part B is outside that wording. We are putting it that way deliberately rather than claiming Medicare states the exclusion, because it does not state it in the negative — it simply defines what the cap counts. The effect on your household budget is the same either way. A person with $2,400 of Part D drugs and a monthly Part B infusion has one capped cost and one uncapped one, and only the capped one appears in the comparison they did in October.

8. What Advantage and Medigap do about it

There are two ways to put a ceiling on the Part B side, and Annual Enrollment is when both are decided. The first is a Medicare Advantage plan, which has a yearly limit on what you pay out of pocket for covered services. Once you reach it, the plan covers 100 percent of covered services for the rest of the year. That limit applies to the medical side, which is where Part B drugs live, so for somebody with an infusion it is often the single most important figure on the plan.⁴

The second is a Medicare Supplement, or Medigap, policy, which sits alongside Original Medicare and picks up cost sharing that Part B otherwise leaves with you — including that 20 percent. We should say plainly that we do not sell Medigap. We explain it because you cannot think about Part B drug exposure honestly without it, and because the choice between Advantage and Medigap is the structural decision underneath all of this.⁶

9. How to find out which part pays for yours

You do not need to memorise any of the categories. Four questions settle it for almost every medication, and you can work through them in an afternoon.

1. Ask yourself who physically gives it to you. If the answer is a nurse, a doctor or an infusion centre, start from Part B. If the answer is you, start from Part D.
2. Look for it on your plan’s formulary. If a drug you take regularly is simply not listed, that absence is a clue rather than a problem — it is often a sign the drug is billed under Part B.
3. Ask the prescriber’s billing office directly. They know which part they bill, because they do it every month. The question to use is: “Do you bill this under Part B or does it go through my drug plan?”
4. Check an Explanation of Benefits from earlier this year. A Part B drug shows up in your Medicare claims, not on your drug plan statement. The paperwork has already answered the question.

10. A South Florida lens

Which of the two structures you are in is not an abstract question in South Florida, because the three counties sit in completely different places. Palm Beach still has more people in Original Medicare than in Medicare Advantage — 192,500 against 177,865. Broward runs the other way at 133,954 to 246,276, and Miami-Dade overwhelmingly so at 129,837 to 394,671. The Palm Beach households are the ones with no annual ceiling unless they bought a supplement, and they are the largest group of the three for whom Part B drug exposure is unlimited by default.⁸

On the Advantage side the ceiling exists but it varies more than people expect. For 2027 the average out-of-pocket maximum across Advantage plans is about $4,824 in Broward, $4,555 in Miami-Dade and $5,114 in Palm Beach, and the highest plan in all three counties sits at $9,850. Two plans that both cost $0 a month can be nearly $5,000 apart on the number that actually governs a bad year. You can check your own county on our Broward, Miami-Dade and Palm Beach pages.⁹

11. What to do before December 7

None of this requires you to become an expert in Medicare billing. It requires you to make sure the comparison you are doing covers all of your medication rather than the part that happens to be easy to price.

1. Write the full list, not the pharmacy list. Add anything you are injected with, infused with, or given at an office visit. That is the part a formulary search will not surface.
2. Sort it into two columns. Collected by you, administered to you. Use the four questions above where you are not sure.
3. Price the Part D column normally, by running it through Plan Compare or by bringing it to us.
4. For the Part B column, compare out-of-pocket maximums instead. On a Medicare Advantage plan that figure is the ceiling. On Original Medicare there is not one, which is the Medigap conversation.
5. Do both before December 7. The window closes then and the structural choice — Advantage or Original Medicare with a supplement — is the hardest one to reverse afterwards.

12. Frequently asked questions

13. Sources

1. Medicare.gov. Prescription drugs (outpatient) — which drugs Part B covers, the rule that Part B covers drugs you would not typically give yourself, the 20 percent coinsurance after the Part B deductible, and the vaccines that cost nothing with no deductible. Read October 16, 2026. medicare.gov — outpatient prescription drugs
2. Medicare.gov. Insulin — the $35 cap on a one-month supply of each covered insulin product under both Part B and Part D, the absence of a deductible, and which delivery methods fall under which part. medicare.gov — insulin
3. Medicare.gov. Medicare drug coverage costs — the out-of-pocket maximum on covered Part D drugs of $2,400 in 2027, the maximum deductible of $700, and what counts toward the cap. medicare.gov — Part D costs
4. Medicare.gov. What does Medicare cost — that there is no yearly limit on out-of-pocket costs under Original Medicare without supplemental coverage, that Medicare Advantage plans do have a yearly limit, and the 20 percent coinsurance on covered services. medicare.gov — what does Medicare cost
5. Medicare.gov. Medicare costs — the 2026 Part B standard premium of $202.90 and annual deductible of $283. medicare.gov — Medicare costs
6. Medicare.gov. Medigap — what a Medicare Supplement policy covers alongside Original Medicare, including Part B coinsurance. medicare.gov — Medigap
7. Medicare.gov. Shingles vaccines — coverage under Part D for adult vaccines recommended by the Advisory Committee on Immunization Practices, at no cost to the enrollee. medicare.gov — shingles vaccines
8. Centers for Medicare & Medicaid Services. Medicare Monthly Enrollment, June 2026 — county-level Original Medicare and Medicare Advantage enrollment for Broward, Miami-Dade and Palm Beach. Read October 12, 2026. data.cms.gov — Medicare monthly enrollment
9. Centers for Medicare & Medicaid Services. CY2027 and CY2026 Medicare Advantage / Part D landscape source files — county-level plan counts and out-of-pocket maximums for Florida. Read October 12, 2026. cms.gov — Part D landscape source files

Disclaimer: JCKC Financial Services is a licensed independent insurance brokerage that also provides tax preparation and notary services. We are not connected with or endorsed by the U.S. government or the federal Medicare program. We do not sell Medicare Supplement (Medigap) policies; where this article describes them it does so for explanation only. Coverage rules, coinsurance, deductibles and the Part D out-of-pocket maximum are set by federal law and CMS and are subject to change; the 2026 Part B premium and deductible are stated because the 2027 figures had not been announced when this was written. Which part of Medicare pays for a particular drug depends on the drug, how it is administered and your own circumstances, and should be confirmed with your plan, your prescriber or on Medicare.gov before you rely on it. This article is general information only and is not legal, tax, financial, medical or insurance advice, or a substitute for guidance from a licensed professional about your specific situation.