B-or-D: A Fast Test for Which Part Pays Your GI Drug

Who gives the drug, and where, usually decides whether Part B or Part D pays.

A pharmacy receipt says one thing. Your benefits statement says another. If you take a drug for Crohn's disease, ulcerative colitis or another GI (digestive) condition, it's common to feel unsure which part of your coverage is supposed to pay for it. You are not alone in that.

One question settles most cases. Who gives you the drug, and where? A drug a clinician infuses or injects in an office or hospital outpatient department usually falls under Part B. A drug you swallow or inject yourself, picked up at a retail pharmacy, usually falls under Part D. People enrolled in both parts can get outpatient drugs through either benefit, and the type of drug and the way it is given decide which one applies. When a new GI prescription is written, it can help to ask the office one thing before you leave: will you give this dose here, or will I pick it up at a pharmacy?

The line between the two sides also carries more weight than it once did. Between 2017 and 2022, national spending on drugs dispensed outside retail settings grew 9.4% a year, compared with 6.5% for drugs sold through retail pharmacies. That growth sits on the Part B side of the line, which is where a few exceptions start to matter.

Which Medicare part pays for my GI medication?

In short: Which Medicare part pays for my GI medication?: Ask who gives the drug.

Ask who gives the drug. If a clinician infuses or injects it in an office, Part B usually pays. If you take it yourself from a pharmacy, Part D usually pays.

If a new prescription from your gastroenterologist (a digestive system specialist) has you unsure, it can help to walk through three plain questions before you call anyone:

1. Who gives the dose? A doctor, nurse or infusion team, or you at home.
2. Where does the drug come from? The office supplies it, or you pick it up at a pharmacy.
3. Where is it given? A doctor's office, an infusion center or a hospital outpatient department, or your own kitchen table.

Clinician, office supply, clinical setting: think Part B. You, pharmacy, home: think Part D. That is the whole idea behind the B-or-D question in this article's title.

The State Health Insurance Assistance Program, known as SHIP, states the core rule plainly: "Part D cannot pay for any drugs that Part B covers." SHIP also explains that which part covers a drug "depends on what the drug is used for and how it's administered." It can help to keep that line handy when you call your plan. So before a new GI drug is billed, it can help to ask the office whether it will supply the dose or send you to a pharmacy.

The common assumption is that Part D, your drug plan, handles every prescription. It does not. Drugs a doctor's office or hospital outpatient department gives as part of your care, such as an infusion, generally belong to Part B, while most drugs you take on your own and fill at a retail pharmacy belong to Part D. The Centers for Medicare & Medicaid Services keeps a reference guide that splits drug coverage across Part A, Part B and Part D, and written guidance for claims contractors on telling Part B and Part D apart dates back to 2006.

Of the 5 sources behind this section, each one that addresses routing ties the payer to how the drug is given. None ties it to the drug's brand name. The research section below walks through where that rule bends. Change the setting, and the payer may change with it.

Here is the thing: drug coverage rarely shows up as one tidy question. One of our advocates in Alabama supported a client through housing deadlines, emergency surgery, a rehab stay and several moves, with paperwork arriving at every turn. It is common for a pharmacy question to land in the middle of a stretch like that, and you are not alone if it feels like too much at once.

If you would like a sense of what outside help looks like, our roundup of Medicare patient advocate services for seniors walks through the options. When you call, one option is to ask the pharmacy and the GI office the same question about who gives the dose, and see whether their answers match.

When can the same GI drug switch between Part B and Part D, and how does that change what I pay in 2026?

In short: When can the same GI drug switch between Part B and Part D, and how does that change what I pay in 2026?: An injectable GI.

An injectable GI drug can land in either part. The setting decides it, and in 2026 that choice moves you between a $283 Part B deductible and a Part D plan deductible.

Injections are where the simple question bends. SHIP spells out three situations, and they matter for anyone on a GI biologic (a drug made from living cells, often given as a shot or infusion):

• Your doctor supplies the drug and injects it in the office because you cannot inject it yourself. Part B pays.
• You buy the injectable at a pharmacy and give it to yourself at home. Part D pays.
• You buy it at a pharmacy and bring it to the office so the doctor can inject it. Part D still pays.

That third case surprises people. The doctor's hands are on the needle, yet the pharmacy purchase keeps it on the Part D side. So I would add one small follow-up to the first question: who bought the dose?

Pills follow the pharmacy path too. The maker of one ulcerative colitis treatment, RINVOQ, describes once-daily dosing in its own materials for doctors. A daily pill you take at home sits on the pharmacy side of the question, though your plan's drug list still decides whether it is covered.

How the GI drug reaches you	Which part usually pays	2026 cost markers to know
Office supplies it and a clinician gives it	Part B	$202.90 monthly premium, $283 yearly deductible, then your share of each dose
Pharmacy fills it and you take it at home	Part D	Plan deductible of up to $615, yearly out-of-pocket cap of $2,100
Pharmacy fills it and the office injects it	Part D	Same Part D deductible and cap

Medicare's 2026 figures set the Part B premium at $202.90 a month and the Part B deductible at $283. On the drug plan side, $615 is the most a standard Part D plan can charge as a deductible, and the yearly out-of-pocket cap is $2,100. A plan may set a lower deductible than that.

Here is why that matters. A switch from office injections to home pens can move you from one set of rules to another. Your costs may rise or fall. Your plan's drug list, not Part B, now decides coverage.

In my view, it is worth asking your GI office how the next dose will be given before any switch happens. If the drug stays on the Part B side, our guide on how Part B cost sharing really works explains the share you may still owe. And if a claim has already gone to the wrong part, the fix starts with a phone call and a few specific documents.

Do patient advocates accept Medicare?

In short: Do patient advocates accept Medicare?: Yes. Some patient advocacy services work directly with Medicare patients, and sorting out which part should pay for a drug is.

Yes. Some patient advocacy services work directly with Medicare patients, and sorting out which part should pay for a drug is exactly the kind of tangle an advocate can help untangle.

Understood Care is one of them. Our service is covered by Medicare, available in all 50 states and delivered virtually. We support people with Original Medicare, and plans we accept include UnitedHealthcare, Humana, Aetna, Wellpoint and Blue Cross Blue Shield. Your advocate is a trained care navigator, backed by a clinical team of board-certified physicians and nurse practitioners, who handles the paperwork, insurance claims and system navigation with you.

It may help to know why a wrong-part claim can feel so slippery. The Medicare Rights Center explains that Part D is provided only through private insurance companies that contract with the federal government, either as a standalone drug plan or as a Medicare Advantage plan with drug coverage. So a Part D problem usually gets fixed with your plan. A Part B problem usually gets fixed with the office that billed it.

When a GI drug claim comes back wrong, one option is to work through these steps at your own pace:

1. Run the question again. Who gave the dose, who supplied it, and where? Write the answer down.
2. Find the bill or denial notice. Note which part it was sent to and the reason given.
3. Call the right party. For an office-given drug, call the billing office. For a pharmacy drug, call your pharmacist and your drug plan.
4. Ask them to bill the other part if your answer from step one points there, and ask what proof they need.
5. Appeal if it still comes back denied. Your GI doctor can help show the drug is medically necessary.

None of these steps is complicated on its own. Together, though, they can mean a week of hold music. That is where many people find it helps to hand the calls to someone else.

I have a lot of respect for how hard our advocates work on cases like these. One advocate in Alabama stayed with a client through hotel vouchers, state legal cases, interstate moves, group homes and help with a security deposit. A drug billing mix-up is a smaller knot, but it is the same kind of work: keep track of every thread and keep pulling until it comes loose.

GI care often brings more than one coverage question at once. If a colonoscopy bill arrived alongside your drug claim, our guide to whether your GI scope counts as screening or diagnostic covers that side. Call 646-904-4027 to talk with an advocate, and have your latest denial letter in hand when you do.

What can I do before my next GI drug bill arrives?

Ask who gives the drug and where it comes from, then check that the bill matches. If that answer changes, the part that pays may change with it.

I expect that one question to matter more each year, not less. Spending on drugs given outside the pharmacy has been climbing faster than spending at the pharmacy counter, and every new way of giving a GI drug can move it from one side of the line to the other. A drug that started as an office infusion may later come as a pen you use at home. When that happens, your costs follow the new setting.

It can help to plan for the Part D side too. If a costly drug hits early in the year, one option is the payment plan built into Part D, which spreads what you owe across the calendar year. On a 2024 episode of the CANCER BUZZ podcast, speakers explained that you can enroll at any point in the plan year, though not at the pharmacy counter, and that plans were supposed to help complete enrollment within 24 hours. So call your plan before the fill, not at the register.

You already know the question to ask. Many people find that knowing it changes how the next phone call with a plan or a billing office goes.