Medicare Coverage for Multiple Sclerosis: DMTs, Infusions, and Early Eligibility

Multiple sclerosis (MS) presents two distinct Medicare challenges. First, many people with MS qualify for Medicare before age 65 through Social Security Disability Insurance—so they navigate the program younger and for longer than the typical beneficiary. Second, MS disease-modifying therapies (DMTs) are among the most expensive drugs in all of medicine, with annual list prices commonly exceeding $90,000, and—exactly as with rheumatoid arthritis biologics—whether a given DMT is covered under Part B or Part D depends entirely on how it is administered. This guide explains MS eligibility, the DMT coverage split, relapse treatment, and the supportive care that MS patients rely on.

Early Medicare Eligibility for MS Through SSDI

Most people associate Medicare with turning 65, but people with MS often qualify earlier. If MS prevents you from working and you qualify for Social Security Disability Insurance (SSDI), you become eligible for Medicare after a waiting period:

• You must be disabled and approved for SSDI.
• Medicare begins 24 months after your SSDI cash benefits start (the SSDI five-month waiting period plus the 24-month Medicare waiting period means roughly 29 months from disability onset in many cases).
• At that point you receive Part A and Part B automatically, and you may enroll in Part D and, in most states, a Medigap policy.

Once you have Medicare through disability, you keep it as long as you remain entitled to SSDI, and it converts seamlessly to age-based Medicare when you turn 65 (with a fresh Medigap open enrollment window at 65—an important second chance to buy supplemental coverage without medical underwriting). For the full disability-to-Medicare pathway, see Social Security Disability Benefits.

One caution for younger beneficiaries: Medigap rights for people under 65 vary by state. Some states require insurers to offer at least one Medigap plan to disabled beneficiaries, others do not, and pricing can be high. This makes the Part B vs. Part D coverage route for DMTs (below) especially consequential for under-65 MS patients who cannot easily buy Medigap.

Diagnosing and Monitoring MS Under Part B

MS diagnosis and monitoring run through Part B at 80 percent coverage after the $257 deductible (2026):

• Neurologist visits — including MS specialists at comprehensive MS centers, covered at 20 percent coinsurance.
• MRI of the brain and spinal cord — the cornerstone of MS diagnosis and monitoring, covered at 20 percent coinsurance. MRIs are repeated periodically to track lesion activity, and the 20 percent share on a $1,000–$3,000 MRI adds up.
• Lumbar puncture and spinal fluid analysis — covered under Part B.
• Evoked potential testing and OCT (optical coherence tomography) — covered under Part B.

Because MS requires lifelong, repeated imaging, the cumulative 20 percent coinsurance on MRIs alone is a strong argument for supplemental coverage.

Disease-Modifying Therapies: The Part B vs. Part D Split

DMTs slow MS progression and reduce relapses. They are extraordinarily expensive, and—this is the key financial fact—they split between Part B and Part D based on how they are given. A clinician-infused DMT is Part B; a self-injected or oral DMT is Part D.

DMTs Covered Under Part B (Infused / Clinician-Administered)

These are given by IV infusion at an infusion center, so Medicare pays under Part B:

• Ocrelizumab (Ocrevus) — IV infusion every 6 months; one of the most-prescribed DMTs
• Natalizumab (Tysabri) — IV infusion every 4 weeks
• Alemtuzumab (Lemtrada) — IV infusion course
• Rituximab (Rituxan / biosimilars) — used off-label for MS, IV infusion
• Ocrelizumab/hyaluronidase (Ocrevus Zunovo) — subcutaneous, clinician-administered

Under Part B you pay 20 percent coinsurance with no annual cap. Ocrevus, for example, carries an annual cost around $70,000; 20 percent is roughly $14,000 per year with no ceiling for a beneficiary lacking supplemental coverage. Site of care matters here too—a hospital outpatient infusion costs more than a freestanding infusion center because of the facility fee.

DMTs Covered Under Part D (Self-Injected / Oral)

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

• Self-injected: ofatumumab (Kesimpta), interferon beta products (Avonex, Rebif, Betaseron, Plegridy), glatiramer acetate (Copaxone and generics)
• Oral: fingolimod (Gilenya), dimethyl fumarate (Tecfidera), diroximel fumarate (Vumerity), teriflunomide (Aubagio), siponimod (Mayzent), ozanimod (Zeposia), ponesimod (Ponvory), cladribine (Mavenclad)

Under the redesigned Part D benefit, out-of-pocket spending is capped at $2,000 per year (2025 onward). A self-injected DMT like Kesimpta or an oral DMT like Tecfidera—each with a five- or six-figure list price—costs you at most $2,000 out of pocket for the year, after which you pay $0. You will typically reach the cap in the first month. The Medicare Prescription Payment Plan lets you spread that $2,000 into monthly installments so you are not hit with the full amount at once. See Medicare Part D Explained for how the cap and formulary tiers work.

The Result: Route of Administration Drives Cost

Just as with Medicare’s biologic coverage for rheumatoid arthritis, the counterintuitive consequence is that a Part D self-injected or oral DMT (capped at $2,000) can be far cheaper than a Part B infused DMT (20 percent, uncapped) for a beneficiary without Medigap:

• Ocrevus (Part B, no Medigap): ~$14,000/year, no cap
• Kesimpta or Tecfidera (Part D): $2,000/year cap

This $12,000 swing is decided purely by whether the drug is infused or self-administered. When a neurologist considers clinically comparable options—say, an infused anti-CD20 (Ocrevus) versus a self-injected anti-CD20 (Kesimpta)—the Medicare coverage route is worth raising as part of the conversation, particularly for under-65 patients who cannot get affordable Medigap.

How Supplemental Coverage Changes the Math

• Medigap Plan G pays the 20 percent Part B coinsurance, so an infused DMT like Ocrevus costs $0 beyond the Part B deductible all year. For someone on IV therapy, this converts a $14,000 uncapped exposure into essentially nothing. Plan G does not touch Part D drugs, but the $2,000 Part D cap handles those. Together they bound your total DMT cost regardless of which drug you take. See Medigap Plans Compared.
• Medicare Advantage caps annual medical out-of-pocket costs (protecting against uncapped infusion coinsurance) but adds prior authorization, step therapy, and network restrictions—your MS center and infusion site must be in network. For a condition managed at a specialized MS center, network freedom often favors original Medicare plus Medigap. See Medicare Advantage vs. Original Medicare.

For under-65 beneficiaries who cannot buy affordable Medigap in their state, a Medicare Advantage plan’s out-of-pocket maximum may be the only practical cap on Part B infusion coinsurance—making MA worth serious consideration in that specific situation.

Treating MS Relapses and Symptoms

• Acute relapse treatment — high-dose IV corticosteroids (methylprednisolone) infused in a clinic are Part B; oral steroid tapers are Part D. Acthar gel and plasma exchange (PLEX) for severe relapses are Part B.
• Symptom management drugs — for spasticity (baclofen, tizanidine), fatigue, bladder dysfunction, neuropathic pain (gabapentin, pregabalin), and walking (dalfampridine/Ampyra) are Part D. Most are inexpensive generics except Ampyra.
• Botulinum toxin injections — for spasticity or overactive bladder, administered by a clinician, are Part B.

Rehabilitation and Supportive Care

MS care extends well beyond drugs, and Medicare covers the rehab that preserves function:

• Physical, occupational, and speech therapy — covered under Part B at 20 percent coinsurance with no hard annual cap (the KX modifier threshold permits continued medically necessary therapy). The Jimmo v. Sebelius settlement confirms Medicare covers therapy to maintain function or slow decline—not only to improve it—which matters enormously in a progressive disease. See Medicare Chronic Pain Management for how the therapy benefit works.
• Durable medical equipment (DME) — wheelchairs, power scooters, walkers, canes, and hospital beds are covered under Part B at 20 percent coinsurance when prescribed as medically necessary. Note Medicare does not pay for home modifications like ramps, widened doorways, or stair lifts.
• Home health care — for homebound patients, skilled nursing and therapy at home are covered at zero cost under Part A/B.
• Mental health — depression is common in MS; outpatient therapy and psychiatry are covered under Part B. See Medicare Mental Health Coverage.

What Medicare Does Not Cover

The biggest gap is long-term custodial care. When MS progresses to the point of needing help with daily activities—bathing, dressing, transferring—Medicare does not pay for assisted living, memory care, or long-term nursing home custodial care. Those costs fall to long-term care insurance, personal savings, or Medicaid. For planning, see Long-Term Care Insurance and Medicaid Planning for Long-Term Care.

Low-Income Assistance

DMT costs should never go unmanaged for low-income beneficiaries. Extra Help (Part D Low-Income Subsidy) cuts oral and self-injected DMT copays to a few dollars; Medicare Savings Programs can cover Part B premiums and the 20 percent coinsurance on infused DMTs and MRIs. The National MS Society and several DMT manufacturers run assistance programs as well. See Medicare Savings Programs.

Cost Comparison: A Year on a DMT

Key Takeaways

• Many people with MS qualify for Medicare before 65 through SSDI, after a 24-month waiting period—and get a fresh Medigap window at 65.
• DMTs split between Part B (infused: Ocrevus, Tysabri—20 percent, no cap) and Part D (self-injected/oral: Kesimpta, Tecfidera—$2,000 annual cap) based solely on administration route.
• Without supplemental coverage, an infused DMT can cost ~$14,000/year while an oral DMT is capped at $2,000—a difference driven entirely by coverage category.
• Medigap Plan G eliminates the Part B coinsurance, making infused DMTs essentially free after the deductible—critical for anyone on IV therapy who can buy it.
• Therapy and DME are covered under Part B (with the Jimmo maintenance standard protecting progressive-disease patients), but long-term custodial care is not covered.
• Extra Help and Medicare Savings Programs dramatically reduce DMT costs for low-income beneficiaries.

For the parallel biologic coverage analysis, see Medicare Coverage for Rheumatoid Arthritis and Biologics. For long-range budgeting, see Healthcare Costs in Retirement.