With Original Medicare, you typically pay 20% of the Medicare-approved amount for chemotherapy after meeting your annual Part B deductible of $257 (in 2025). What that 20% actually costs in dollars varies enormously depending on the type of cancer, the drugs used, and how many cycles you need. Some regimens run a few thousand dollars total, while others exceed $100,000 over a full course of treatment, meaning your 20% share could range from a few hundred dollars to tens of thousands.
How Part B Covers IV Chemotherapy
Most chemotherapy given through an IV in a doctor’s office, outpatient clinic, or hospital outpatient setting falls under Medicare Part B. Once you’ve paid the $257 annual deductible, Medicare picks up 80% of the approved amount and you’re responsible for the remaining 20%. That 20% coinsurance applies to the chemotherapy drugs themselves, the administration fees for infusing them, and related services like anti-nausea medications given during treatment.
The critical detail many people miss: Original Medicare has no annual cap on out-of-pocket spending. If your 20% coinsurance adds up to $15,000 or $30,000 over months of treatment, there’s no built-in ceiling that stops the bills. This is one of the biggest financial risks for cancer patients on Original Medicare without supplemental coverage.
Oral Chemotherapy Under Part D
Not all chemotherapy is given by IV. Many newer cancer treatments come as pills you take at home, and these typically fall under Medicare Part D (your prescription drug plan) rather than Part B. Part D plans have their own deductibles, copays, and coverage tiers, and specialty cancer drugs often land on the highest cost-sharing tier.
Starting in 2025, a major change helps here. The Inflation Reduction Act capped annual out-of-pocket spending under Part D at $2,000. Before this change, patients taking expensive oral chemotherapy could face bills of $10,000 or more per year for a single medication. The new $2,000 cap means that once you hit that threshold in a given year, you pay nothing more for Part D drugs. For anyone on oral chemotherapy, this is a significant financial protection that didn’t exist before.
Inpatient Chemotherapy Costs
If you’re admitted to the hospital and receive chemotherapy as an inpatient, those costs fall under Medicare Part A instead of Part B. Part A uses a different cost-sharing structure: you pay a deductible per benefit period ($1,676 in 2025) rather than a percentage of each service. For hospital stays up to 60 days, you pay nothing beyond that deductible. Longer stays add daily copays.
Most chemotherapy happens on an outpatient basis, so Part B’s 20% coinsurance is the more common scenario. But patients who need hospitalization during treatment, whether for the chemo itself or for complications, should expect the Part A deductible to apply each time a new benefit period begins.
Medicare Advantage Plans Work Differently
If you have a Medicare Advantage plan (Part C) instead of Original Medicare, your cost-sharing for chemotherapy follows your plan’s specific rules rather than the standard 20% coinsurance. Some plans charge flat copays per treatment session, others use coinsurance percentages that may be higher or lower than 20%.
The key advantage: every Medicare Advantage plan must include an annual out-of-pocket maximum. Once you hit that limit, the plan covers 100% of your Part A and Part B services for the rest of the year. These maximums vary by plan but provide a hard ceiling on your costs, something Original Medicare does not offer. For someone facing months of chemotherapy, this cap can be the difference between manageable bills and financial crisis. Check your plan’s specific maximum, and note whether it differs for in-network versus out-of-network providers.
How Medigap Reduces Your Share
Medicare Supplement Insurance (Medigap) policies are designed to fill the gaps in Original Medicare, and the 20% chemotherapy coinsurance is exactly the kind of gap they cover. Most Medigap plans pay all or part of that 20%, which can save thousands of dollars during cancer treatment. Some plans also cover the Part B deductible.
The catch is timing. You need to purchase a Medigap policy before you’re diagnosed. During your initial enrollment period (when you first sign up for Medicare Part B), insurers must sell you a policy regardless of your health. Outside that window, they can deny coverage or charge more based on pre-existing conditions in most states. If you already have a Medigap plan when cancer is diagnosed, your coinsurance costs for chemotherapy may be fully covered.
Related Treatment Costs
Chemotherapy rarely happens in isolation. Radiation therapy, which many patients receive alongside or after chemo, follows the same Part B cost-sharing rules: 20% coinsurance after the deductible for outpatient treatment. Lab work, imaging scans, and doctor visits during treatment also carry their own Part B coinsurance.
Supportive medications matter too. Anti-nausea drugs given during your infusion session are typically covered under Part B along with the chemotherapy itself. Oral anti-nausea medications you take at home in the 24 to 48 hours surrounding treatment are also covered under Part B as part of the chemotherapy benefit, not under Part D. This is a useful distinction because it means those drugs fall under the 20% coinsurance rather than your prescription plan’s potentially different cost-sharing.
Financial Assistance Options
If costs are overwhelming, Medicare’s Extra Help program can significantly reduce what you pay for Part D prescription drugs, including oral chemotherapy. To qualify in 2025, your annual income must be below $23,475 for an individual or $31,725 for a couple, and your resources (savings, investments, real estate other than your home) must be under $18,090 for an individual or $36,100 for a couple. You apply through Social Security.
Beyond Extra Help, many pharmaceutical manufacturers offer patient assistance programs that cover copays or provide drugs at no cost to Medicare beneficiaries who meet income guidelines. Nonprofit organizations like the Patient Advocate Foundation and CancerCare also offer copay assistance grants. Your oncology office’s financial counselor, if one is available, can help identify which programs apply to your specific drugs and situation.