Does Medicare Cover Keytruda? (And Does Medicaid?)

The Short Answer: Covered, Through Two Different Doors

Search results for "does Medicare cover Keytruda" and "does Medicaid cover Keytruda" both tend to land on the same one-word answer — yes — and then move straight to a generic cost table. That's not wrong, but it skips the part that actually determines what you'll experience at the infusion center: Medicare and Medicaid don't cover Keytruda the same way, don't use the same rules to decide your cost-sharing, and — if you have both — don't even interact the way most people assume.

Medicare's coverage runs through Part B, the medical benefit that also pays for doctor visits and outpatient procedures, because Keytruda is administered by a healthcare provider rather than picked up at a pharmacy counter. Medicaid's coverage runs through a completely different legal mechanism: a 1990 federal rebate law that makes covering FDA-approved drugs from participating manufacturers close to mandatory for states that choose to offer a drug benefit (which, in practice, is all fifty states). Neither program is "optional" for Keytruda in the way people sometimes fear when they read about prior authorization denials — but neither one hands you a simple flat copay, either. The rest of this guide walks through exactly how each path works, and what happens when you're on both at once.

Why Keytruda Is a Medicare Part B Drug, Not Part D

Medicare splits drug coverage across different parts depending on how and where a medication is given, and this single distinction explains most of the confusion people run into. Keytruda (pembrolizumab) is given as an intravenous infusion — or, since late 2025, as a subcutaneous injection via Keytruda Qlex — by a healthcare provider, typically in an oncologist's office, an infusion center, or a hospital outpatient department. Drugs administered that way are billed under Medicare Part B, the medical benefit, using HCPCS billing code J9271 (one billable unit equals 1 mg of pembrolizumab).

This distinction is more than trivia. Medicare's newer, more generous protections — most notably the $2,100 annual out-of-pocket cap on covered prescriptions introduced for 2026 — apply specifically to Part D. Original Medicare's Part B benefit does not have an equivalent annual ceiling. There is a narrower protection: by law, a beneficiary's cost-sharing for a Part B drug or service delivered in a hospital outpatient department on a single day can't exceed the Part A inpatient deductible ($1,736 in 2026), but that specific cap doesn't apply to drugs administered in a physician's office, and neither version limits your total spending across a full year of treatment the way the Part D cap does.

For the full breakdown of what that actually costs by coverage type — commercial insurance, Medicare Advantage, traditional Medicare with and without a supplemental plan — see our Keytruda cost guide, which works through the dollar figures in detail rather than repeating them here.

Original Medicare vs. Medigap vs. Medicare Advantage

Coverage is consistent across every flavor of Medicare — Keytruda is a covered Part B drug regardless of which path you take through the program. What changes dramatically is your cost-sharing structure, and it's worth being precise about the mechanics rather than just citing dollar ranges.

For 2026, CMS set the standard Medicare Part B monthly premium at $202.90 and the annual Part B deductible at $283. Once you've met that deductible, Original Medicare pays 80% of the Medicare-approved amount for a covered Part B drug, and you're responsible for the remaining 20% coinsurance — with no annual ceiling on that coinsurance if you have no supplemental coverage. One nuance worth knowing: Medicare's "approved amount" for Part B drugs is calculated from a formula tied to the drug's average sales price (ASP), not the manufacturer's published list price, so your coinsurance is based on a different, typically lower, number than the sticker price you might see quoted elsewhere.

• Original Medicare with no supplemental coverage — you're exposed to the full 20% coinsurance on every infusion, with no annual cap under Part B.
• Original Medicare plus a Medigap (Medicare Supplement) policy — most Medigap plans cover some or all of the Part B coinsurance, which is precisely why supplemental coverage matters disproportionately for an expensive, recurring infused drug like this one.
• Medicare Advantage (Part C) — plans can charge no more than 20% coinsurance for in-network Part B drugs, and unlike Original Medicare, they're required to have an annual out-of-pocket maximum. That limit is separate from, and structured differently than, the Part D cap; average in-network maximums have run in the low five-thousand-dollar range in recent years, though the exact figure is plan-specific and changes annually.

None of these mechanics change whether Keytruda is covered — only how much of the bill lands on you. If you're weighing Medigap versus Medicare Advantage specifically because of a Keytruda prescription, that coinsurance-versus-out-of-pocket-cap tradeoff is the central thing to understand, more than any plan marketing material about "extra benefits."

The Extra Help Mix-Up That Costs People Real Money

Here's a confusion we see constantly, and it's different from (though related to) the $2,100 Part D cap issue: people who qualify for Extra Help — Medicare's Part D Low-Income Subsidy — sometimes assume it will reduce their Keytruda bill, because Extra Help is broadly marketed as "help paying for your Medicare drugs." It's a legitimate, valuable program. It just doesn't apply here.

So what does help a low-income Medicare beneficiary with Part B cost-sharing on a drug like Keytruda? That's a different, less-publicized set of programs — covered next.

Medicare Savings Programs: The Real Fix for Low-Income Beneficiaries

The programs that actually reduce Part B cost-sharing are the Medicare Savings Programs (MSPs), which are administered by each state's Medicaid agency but are legally and functionally distinct from full Medicaid enrollment. There are three main tiers, and only one of them covers coinsurance.

QMB is the one that matters for a drug like Keytruda. If you qualify, your state's Medicaid program pays your Medicare Part A and Part B premiums, deductibles, coinsurance, and copayments — in effect functioning like a built-in Medigap policy, without the monthly Medigap premium. Income limits are set relative to the Federal Poverty Level and adjusted annually; as of 2026, most states set the QMB income limit for a single applicant at roughly $1,325 to $1,350 a month, with asset limits in the range of several thousand dollars, though a handful of states use higher or no asset limits at all. Because exact figures vary slightly by state and change every year, confirming the current number with your state Medicaid office is worth doing directly rather than relying on any single published figure, including this one.

SLMB and QI have higher income ceilings than QMB but only cover the Part B premium — not deductibles or coinsurance — so they won't reduce what you pay per infusion. If your income is a little too high for QMB, it's still worth applying for whichever program you do qualify for, since even premium-only relief adds up, and some states don't count certain income or assets the way the federal baseline does. Applications go through your state Medicaid office, not through Medicare directly, and even a partial-year approval is sometimes retroactive.

Dual Eligible? Here's Why "$4 to $8" Might Be Your Number Too

You'll see the figure "Medicaid patients typically pay $4 to $8 per infusion" repeated across pricing pages, including our own cost guide, sourced from Medicaid.gov's federal cost-sharing rules. What most of those pages don't spell out is that this figure often applies to a second group as well: people enrolled in both Medicare and Medicaid, commonly called dual eligibles.

Here's the mechanism. If you're a full dual eligible, Medicare pays first, as your primary insurer, exactly as it would for any Medicare beneficiary — the same Part B rules, same 20% coinsurance calculation described above. Medicaid then steps in as your secondary payer and picks up that remaining coinsurance, subject to your state's own nominal Medicaid cost-sharing rules, which is where a low, flat figure like $4 to $8 typically comes from rather than the full 20% coinsurance amount. QMB enrollees who also have full Medicaid benefits (sometimes called "QMB Plus") get this same protection through the QMB billing prohibition described above.

One related program worth knowing about if you're a dual-eligible senior with significant care needs: the Program of All-Inclusive Care for the Elderly (PACE) coordinates Medicare and Medicaid benefits, including medications, for eligible older adults who might otherwise need nursing-home-level care but wish to remain at home. It's a narrower fit than QMB or standard dual eligibility, but it's another avenue worth asking about if you're navigating both programs simultaneously and want a single coordinated point of contact.

None of this changes the guidance in our Keytruda savings card guide: Merck's manufacturer copay card explicitly excludes anyone on Medicare, Medicaid, or another government program, dual eligible or not. The coverage mechanics above are what actually helps this group — not a manufacturer coupon.

Does Medicaid Cover Keytruda? The Federal Rule That Makes It Automatic

Here's the part most "yes, Medicaid covers it" articles never explain: why is coverage so consistent, when Medicaid is a state-run program with fifty different sets of rules for almost everything else?

The answer is the Medicaid Drug Rebate Program (MDRP), created by a 1990 federal law. Outpatient prescription drug coverage is technically an optional Medicaid benefit — but every state has chosen to offer it, and once a state does, the rebate program's terms kick in: a drug manufacturer that signs a National Drug Rebate Agreement with HHS, agreeing to pay rebates on drugs used by Medicaid patients, gets something significant in return — state Medicaid programs are then required to cover essentially all of that manufacturer's FDA-approved outpatient drugs. As one Medicaid policy association puts it plainly, in exchange for the rebate, "states must cover nearly all FDA-approved outpatient drugs from participating manufacturers," and Medicaid agencies "cannot outright deny coverage of most drugs."

Merck participates in this program — you can see the practical evidence of that on Merck's own Keytruda financial support page, which cites Medicaid.gov's federal cost-sharing guidance directly as the source for what Medicaid patients pay. That's only possible because Medicaid is, in fact, covering the drug nationwide.

That utilization management piece is real, though. A 2024 CMS rule went further and now requires states to collect detailed National Drug Code information specifically on physician-administered drugs like Keytruda, and to actively invoice manufacturers for the rebates owed on them — a sign that regulators have been tightening, not loosening, oversight of exactly this category of high-cost infused drug within Medicaid.

Where States Actually Differ (It's Not Coverage)

Because the underlying coverage obligation is federal, the meaningful state-to-state differences show up in the utilization management layer, not in whether Keytruda appears on a formulary at all. State Medicaid clinical policies for pembrolizumab can run dozens of pages, covering nearly every FDA-approved indication individually, with separate dosing rules by age group.

As one concrete example: Louisiana's Medicaid pembrolizumab clinical policy — a publicly posted document, not a generic summary — spells out coverage criteria indication by indication, including specific pediatric dosing limits (for instance, capping certain pediatric indications at defined milligram totals per cycle, tied directly to FDA labeling and pharmaceutical compendia). That level of granularity is typical of how states manage a drug this expensive and this broadly indicated: not by blocking access, but by tightly specifying exactly which diagnosis, stage, and dose qualifies.

If your Medicaid prior authorization request for Keytruda is denied, the underlying reasons tend to mirror what we cover in detail in our Keytruda prior authorization guide for commercial and Medicare Advantage plans — missing biomarker documentation, an indication that isn't clearly supported by the label or compendia listing, or a dosing request that exceeds the state's specified limit — rather than an outright non-coverage decision.

Medicaid Managed Care vs. Fee-for-Service

Most Medicaid beneficiaries nationally are enrolled in a managed care organization (MCO) rather than traditional fee-for-service Medicaid, and the federal rebate rule's mandatory-coverage requirement extends to MCO-dispensed drugs as well — an MCO can't sidestep the obligation just because it's a private plan administering the state's Medicaid benefit. What can differ is the specific paperwork: your MCO or its pharmacy benefit manager may run its own prior authorization portal and documentation checklist for Keytruda, separate from the state's own fee-for-service policy, even though both are ultimately bound by the same federal coverage floor.

Practically, this means the fastest way to find your exact requirements isn't a general Medicaid.gov search — it's asking your specific MCO (or your oncology practice's financial counselor, who deals with this daily) which portal and criteria apply to your plan.

The 2025 Law Quietly Delaying a Lower Medicare Price

This is the piece of current, dated information that changes the "will my cost go down soon" answer, and it's recent enough that a lot of coverage content hasn't caught up to it.

The Inflation Reduction Act created the Medicare Drug Price Negotiation Program, which lets the federal government negotiate lower prices for certain high-spending drugs — and Part B drugs like Keytruda became eligible for this process starting with prices effective in 2028. Because of its enormous Medicare spending — Keytruda ranked as the single highest-spending drug in Medicare's entire Part B program in 2023, at $12,600 per claim and roughly $76,100 per user that year, according to CMS spending data analyzed by KFF — health policy analysts widely expected it to be selected for negotiation in the program's near-term rounds.

A 2025 tax and budget reconciliation law changed that calculus. It expanded an existing "orphan drug exclusion" that shields certain rare-disease drugs from price negotiation. Keytruda's original 2014 FDA approval was for melanoma, granted under an orphan drug designation, before it was approved just over a year later for a much broader, non-orphan use in non-small cell lung cancer — and dozens of additional cancer indications since. Under the law's revised rules, the clock that determines Keytruda's eligibility for negotiation now effectively restarts later, delaying its eligibility for selection from what would have been 2026 to 2027 at the earliest — which means a negotiated price, if selected, wouldn't take effect until 2029 rather than 2028.

None of this affects whether Medicare covers Keytruda — it affects the price your 20% coinsurance is calculated against, for longer than originally expected. It also has no bearing on Medicaid pricing, since the Medicare negotiation program is entirely separate from the Medicaid rebate mechanism described earlier. If you want the fuller pricing context, including how this same delay affects the "is Keytruda getting cheaper" question more broadly, see the dedicated section in our Keytruda cost guide.

Off-Label and Edge-Case Uses

Keytruda carries an unusually large number of FDA-approved indications, but both Medicare and Medicaid coverage decisions can also reach beyond the strict FDA label in certain cancer-treatment contexts. Medicare rules specifically allow coverage determinations for anti-cancer drugs to rely on recognized clinical compendia — most notably the NCCN Drugs & Biologics Compendium — when a specific use isn't explicitly spelled out in the FDA label but is supported by established oncology guidelines. State Medicaid programs commonly build their own clinical policies around the same compendia.

In practice, this widens coverage in genuinely useful ways for less common tumor types or combination regimens, but it also means a reviewer checking your prior authorization request is looking at more than the FDA package insert — they're checking whether your specific diagnosis, staging, and biomarker results line up with compendia-supported use. Our prior authorization guide covers exactly how that review process works, who conducts it, and how long it's allowed to take by plan type.

Does Coverage Change for Keytruda Qlex?

In September 2025, the FDA approved Keytruda Qlex (pembrolizumab and berahyaluronidase alfa-pmph), a subcutaneous injection version that can be given in one to two minutes instead of the roughly 30-minute IV infusion standard Keytruda requires. It carries its own distinct billing code, J9277, separate from IV Keytruda's J9271.

Because it's a legally and administratively separate product, Keytruda Qlex generally needs its own coverage determination from a Medicare Advantage plan or a state Medicaid program — an existing approval for IV Keytruda doesn't automatically carry over. In practice, Medicare and Medicaid programs have generally extended comparable coverage to Qlex under the same broad set of indications, but because it's still a relatively new product, some plans and state Medicaid policies may not have finished building a dedicated coverage policy for it yet. If your oncology team is considering a switch to Qlex, it's worth confirming directly with your specific plan or state Medicaid program whether a coverage determination is already on file, rather than assuming the existing IV authorization applies.

Which Path Applies to You?

Common Mistakes About Keytruda Coverage

Quick Checklist Before Your First Infusion