Medicare Coverage for Rheumatoid Arthritis and Biologics: Part B vs. Part D

Rheumatoid arthritis (RA) is one of the most expensive chronic conditions to treat under Medicare, and the reason is the drugs. The biologic and targeted synthetic medications that have transformed RA care over the past two decades carry list prices of $5,000 to $7,000 per month. For a Medicare beneficiary, the single most important financial question is not whether these drugs are covered—most are—but which part of Medicare pays for them. The same biologic can fall under Part B or Part D depending only on how it is given, and that distinction can mean a difference of tens of thousands of dollars in out-of-pocket cost per year.

This guide walks through every layer of RA treatment under Medicare: diagnosis, conventional DMARDs, the infused biologics under Part B, the self-injected and oral agents under Part D, and the coverage strategy that protects you from the worst of the cost exposure.

Diagnosing RA Under Medicare Part B

Rheumatoid arthritis is diagnosed and monitored by a rheumatologist, and those visits are covered under Medicare Part B at 80 percent of the approved amount after you meet the annual Part B deductible ($257 in 2026). You pay the remaining 20 percent coinsurance unless you have supplemental coverage.

The diagnostic workup is also Part B:

• Blood tests — rheumatoid factor (RF), anti-CCP antibodies, ESR, and C-reactive protein are clinical laboratory tests covered at zero cost-sharing (no deductible, no coinsurance).
• Imaging — X-rays of the hands and feet, joint ultrasound, and MRI to assess erosions and synovitis are covered at 20 percent coinsurance after the deductible.
• Joint aspiration and corticosteroid injection — covered as Part B procedures at 20 percent coinsurance.

Ongoing monitoring (periodic labs to track disease activity and screen for drug toxicity) continues under Part B for as long as you are treated.

Conventional DMARDs: Almost Always Part D

The first-line treatment for RA is a conventional synthetic disease-modifying antirheumatic drug (DMARD). These are inexpensive oral medications, and because you take them yourself at home, they are covered under Medicare Part D:

• Methotrexate — the anchor drug for RA, a Tier 1 generic typically costing $5–$20 per month
• Hydroxychloroquine (Plaquenil) — Tier 1 generic, $5–$15 per month
• Sulfasalazine — Tier 1 generic, $10–$25 per month
• Leflunomide (Arava) — generic, low-tier

These drugs rarely create financial stress. The picture changes completely when conventional DMARDs fail to control the disease and a rheumatologist escalates to a biologic. To understand why the next decision matters so much, see Medicare Part B vs. Part D Drugs, which explains the coverage split that governs every biologic.

The Critical Split: Infused Biologics (Part B) vs. Self-Injected and Oral Biologics (Part D)

Here is the rule that determines your cost. A drug administered to you by a clinician—infused intravenously or injected in a doctor’s office or infusion center—is covered under Part B as a physician-administered drug. A drug you inject yourself at home or take by mouth is covered under Part D. RA biologics exist in both categories, and the financial consequences are dramatically different.

Biologics Covered Under Part B (Infused / Office-Administered)

These are given by IV infusion or by a clinician, so Medicare pays for them under Part B:

• Infliximab (Remicade) and its biosimilars (Inflectra, Avsola, Renflexis) — IV infusion every 4–8 weeks
• Rituximab (Rituxan) and biosimilars (Ruxience, Truxima, Riabni) — IV infusion in two doses, repeated every ~6 months
• Abatacept (Orencia) — available as a monthly IV infusion (Part B) or a weekly self-injected pen (Part D)
• Tocilizumab (Actemra) — IV infusion (Part B) or subcutaneous self-injection (Part D)
• Golimumab IV (Simponi Aria) — IV infusion, Part B (note: the subcutaneous Simponi is Part D)

Under Part B, you pay 20 percent coinsurance with no annual out-of-pocket cap. For a drug like infliximab, a single infusion can run $3,000–$5,000 depending on dose and biosimilar; 20 percent of that is $600–$1,000 per infusion, repeated every 4–8 weeks indefinitely. Over a year, a beneficiary with no supplemental coverage can face $7,000–$12,000 in coinsurance for a single Part B biologic. There is no ceiling under Part B alone.

The site of care also matters. The same infusion costs more in a hospital outpatient department than in a freestanding infusion center or physician office, because the facility fee is higher. Asking to be infused at a physician’s office or independent infusion suite, when clinically appropriate, can meaningfully lower your 20 percent share.

Biologics and Targeted Drugs Covered Under Part D (Self-Injected / Oral)

These you administer yourself, so they fall under Part D:

• Adalimumab (Humira) and biosimilars (Amjevita, Hyrimoz, Cyltezo, and others) — self-injected pen
• Etanercept (Enbrel) — self-injected pen
• Certolizumab (Cimzia) — self-injected
• Golimumab SC (Simponi) — self-injected
• Sarilumab (Kevzara) — self-injected
• Subcutaneous abatacept (Orencia) and tocilizumab (Actemra) — self-injected versions
• JAK inhibitors (oral): tofacitinib (Xeljanz), baricitinib (Olumiant), upadacitinib (Rinvoq) — daily pills

Under the redesigned Part D benefit, out-of-pocket spending is capped at $2,000 per year (2025 onward). Once your true out-of-pocket costs reach that cap, you pay nothing more for covered drugs for the rest of the year. For a drug like Humira or Rinvoq with a list price exceeding $70,000 per year, this cap is the single most valuable protection in modern Medicare. You will typically hit the $2,000 cap within the first month or two and then pay $0 for the remainder of the year. The Medicare Prescription Payment Plan also lets you spread that $2,000 across monthly installments. For the mechanics of the cap and how to read a formulary, see Medicare Part D Explained.

The Counterintuitive Result: Part D Is Often Cheaper Than Part B for Biologics

This is the part that surprises most beneficiaries. Because Part D now has a hard $2,000 annual cap and Part B has no cap, a self-injected biologic (Part D, capped at $2,000) can cost far less out of pocket than an infused biologic (Part B, 20 percent forever) for a beneficiary who does not have Medigap.

Consider two beneficiaries with the same RA severity:

• Beneficiary A is prescribed infliximab (Remicade), infused every 6 weeks. Under Part B with no Medigap, she pays 20 percent of roughly $35,000 in annual drug-plus-administration cost — about $7,000 per year, with no ceiling.
• Beneficiary B is prescribed adalimumab (Humira), self-injected. Under Part D, his out-of-pocket cost is capped at $2,000 per year.

Same disease, same drug class, $5,000 difference—driven entirely by the route of administration and which part of Medicare pays. This is why, when two clinically equivalent options exist (as they do for abatacept and tocilizumab, which come in both IV and subcutaneous forms), the coverage route is worth discussing with your rheumatologist.

The exception is when you carry comprehensive Medigap. Then the calculus flips, because Medigap erases the Part B coinsurance entirely.

How Medigap Changes the Math

If you have Medigap Plan G (or Plan F for those eligible before 2020), your plan pays the 20 percent Part B coinsurance on infused biologics. That means a Part B drug like infliximab or rituximab costs you $0 beyond the Part B deductible for the entire year, no matter how many infusions you need. For someone on a high-cost infused biologic, Medigap is transformative: it converts an uncapped $7,000–$12,000 annual exposure into essentially nothing.

Medigap does not cover Part D drugs—your self-injected and oral biologics still run through your Part D plan and its $2,000 cap. But between Plan G covering Part B drugs and the Part D cap covering self-administered drugs, a beneficiary with both has predictable, bounded costs across every RA treatment path. To compare the standardized Medigap options, see Medigap Plans Compared, and for the head-to-head cost analysis, Medicare Supplement vs. Advantage Costs.

Medicare Advantage and RA: Prior Authorization Is the Catch

Medicare Advantage (MA) plans cover the same biologics, and MA plans do have an annual out-of-pocket maximum on medical (Part B) services—which can protect against uncapped infusion coinsurance. But there are real trade-offs for RA patients:

• Step therapy — most MA plans require you to fail one or more preferred biologics before approving the one your rheumatologist wants.
• Prior authorization — nearly every biologic, infused or self-injected, requires prior authorization, and approvals can be delayed or denied.
• Network limits — your rheumatologist and preferred infusion center must be in network.
• Specialty drug tiers — self-injected biologics often sit on a specialty tier with high coinsurance until the Part D cap is reached.

For a complex, lifelong condition like RA, the freedom to see any rheumatologist and the predictability of Medigap often outweigh the lower premiums of MA. The right answer depends on your finances and how settled your treatment plan is. See Medicare Advantage vs. Original Medicare for the full comparison.

Other RA-Related Coverage

• Physical and occupational therapy — covered under Part B at 20 percent coinsurance, with no hard annual cap (the KX modifier threshold allows continued coverage when medically necessary). RA patients often need OT for hand function and joint protection. See Medicare Chronic Pain Management for how therapy coverage works.
• Corticosteroids — oral prednisone is a cheap Part D generic; injected corticosteroids given in the office are Part B.
• Bone protection — long-term steroid use raises osteoporosis risk; DEXA scans and osteoporosis drugs are covered as described in Medicare Coverage for Osteoporosis.
• Joint replacement — when RA destroys a hip or knee, surgery is covered under Part A/B.

Low-Income Assistance

Beneficiaries with limited income should not pay full freight for RA drugs. Extra Help (the Part D Low-Income Subsidy) reduces self-injected and oral biologic copays to a few dollars, and Medicare Savings Programs can cover Part B premiums and the 20 percent coinsurance on infused biologics. Many biologic manufacturers also run patient assistance programs, though Medicare beneficiaries generally cannot use manufacturer copay cards. See Medicare Savings Programs for eligibility and how the benefits stack.

Cost Comparison: A Year on a Biologic

Key Takeaways

• RA’s cost is driven almost entirely by biologics, and the route of administration decides whether Medicare pays under Part B (infused) or Part D (self-injected/oral).
• Part B biologics carry 20 percent coinsurance with no annual cap—potentially $7,000–$12,000/year without supplemental coverage.
• Part D biologics are capped at $2,000 per year out of pocket, often making self-injected drugs far cheaper for beneficiaries without Medigap.
• Medigap Plan G eliminates the Part B coinsurance, making infused biologics essentially free after the deductible—the best protection for anyone on IV therapy.
• Medicare Advantage caps medical out-of-pocket costs but imposes step therapy, prior authorization, and network limits that can complicate RA care.
• Conventional DMARDs (methotrexate, hydroxychloroquine) are cheap Part D generics and rarely a financial concern.

For the broader picture of budgeting for a chronic condition in retirement, see Healthcare Costs in Retirement. To understand the coverage split that governs every biologic decision, start with Medicare Part B vs. Part D Drugs.