Psoriasis and its joint-affecting cousin, psoriatic arthritis, are lifelong autoimmune conditions that often persist or worsen into the Medicare years. Mild cases are managed with creams and light therapy, but moderate-to-severe disease increasingly means biologic drugs—some of the most expensive medications in all of Medicare. Whether one of those biologics costs you a few hundred dollars a year or many thousands comes down to a single technical detail: how the drug is administered. This guide explains exactly what Medicare covers, where your costs come from, and how the right supplemental coverage protects you.

Diagnosis and Routine Care Under Part B

Most psoriasis and psoriatic arthritis care runs through Part B at 80 percent after the $257 deductible (2026), leaving you 20 percent coinsurance:

  • Dermatologist and rheumatologist visits — 20 percent coinsurance per visit
  • Skin biopsy to confirm psoriasis or rule out other conditions — 20 percent coinsurance
  • Joint imaging (X-ray, ultrasound, MRI) and lab work (inflammatory markers, screening before starting biologics) for psoriatic arthritis
  • Tuberculosis and hepatitis screening before biologic therapy—required because these drugs suppress the immune system

For psoriatic arthritis, the same disease-modifying logic applies as in other inflammatory arthritis. Our guide to Medicare and rheumatoid arthritis biologics covers the joint-protection side in depth, and much of it carries over.

Topicals and Phototherapy

For mild-to-moderate psoriasis, first-line treatment is usually:

  • Topical drugs — corticosteroid creams, vitamin D analogs (calcipotriene), tazarotene, and newer non-steroidal options (roflumilast, tapinarof). These are filled at the pharmacy under Part D, generally at low generic or mid-tier copays.
  • Phototherapy (UVB light treatment) — administered in a dermatology office under Part B at 20 percent coinsurance, typically two to three sessions a week for a course. Home phototherapy units can sometimes be covered as durable medical equipment with documentation.

These options are inexpensive relative to biologics, and many beneficiaries are managed on them for years.

The Core Cost Split: Infused (Part B) vs. Self-Injected (Part D) Biologics

When topicals and light therapy aren’t enough, treatment escalates to biologics, and here the single most important financial fact takes over: the route of administration determines which part of Medicare pays and how much you owe. This is the same Part B vs. Part D drug split that drives cost across serious diagnoses.

Infused biologics — Part B, no annual cap

Biologics given by IV infusion in a clinic or hospital outpatient department fall under Part B, where you owe 20 percent coinsurance with no annual limit:

  • Infliximab (Remicade and biosimilars) — given every six to eight weeks after loading
  • Intravenous abatacept (Orencia IV) and other infused options used for psoriatic arthritis

At roughly $1,000–$2,000 per infusion, a year of maintenance infliximab can mean $1,500–$3,000 or more in coinsurance—every year, with no ceiling.

Self-injected and oral drugs — Part D, capped at $2,000

The majority of modern psoriasis and psoriatic arthritis biologics are self-injected at home with a prefilled pen or syringe, which places them under Part D:

  • TNF inhibitors — adalimumab (Humira and biosimilars), etanercept (Enbrel), certolizumab (Cimzia), golimumab (Simponi)
  • IL-17 inhibitors — secukinumab (Cosentyx), ixekizumab (Taltz), bimekizumab (Bimzelx)
  • IL-23 inhibitors — guselkumab (Tremfya), risankizumab (Skyrizi), tildrakizumab (Ilumya)
  • IL-12/23 inhibitor — ustekinumab (Stelara and biosimilars), self-injected for maintenance
  • Oral agents — apremilast (Otezla), deucravacitinib (Sotyktu), and JAK inhibitors (upadacitinib/Rinvoq, tofacitinib/Xeljanz) for psoriatic arthritis

These carry eye-watering list prices—commonly $6,000–$10,000 per month—but under the 2025 Part D redesign, your total annual out-of-pocket for all covered Part D drugs is capped at $2,000, with the option to spread it over the year through the Medicare Prescription Payment Plan. See our Part D guide for how the cap and tiers work.

The counterintuitive result

A patient on a $9,000-a-month self-injected IL-17 biologic under Part D pays no more than $2,000 a year, while a patient on infused infliximab under Part B can owe several thousand dollars a year with no cap—even though infliximab is often the cheaper drug by list price. The administration route, not the price tag, drives your bill. It is genuinely worth asking your dermatologist or rheumatologist whether a self-injected or oral option is appropriate for you, and what each would cost under your specific coverage. (Note: a drug self-injected at home is Part D, but the same drug administered in the office can sometimes be billed under Part B—so where you receive it matters too.)

A Concrete Cost Example

Consider two beneficiaries, each on a biologic costing about $7,000 a month, both with Original Medicare and a Part D plan but no supplement:

  • Beneficiary A — self-injected biologic (Skyrizi) under Part D. Total out-of-pocket is capped at $2,000 for the entire year, no matter how many doses. They can spread that $2,000 into level monthly payments through the Medicare Prescription Payment Plan.
  • Beneficiary B — infused infliximab under Part B. At roughly $1,500 per infusion every eight weeks (about seven infusions a year), 20 percent coinsurance comes to roughly $2,100 a year—and it repeats every year with no cap. Add the office-visit coinsurance and it climbs higher.

Now give both beneficiaries Medigap Plan G: Beneficiary B’s Part B coinsurance drops to essentially zero (after the small annual deductible), while Beneficiary A’s Part D cost is unchanged at $2,000. The supplement only helps the Part B side—which is exactly where the uncapped risk lives.

What Medicare Does Not Cover

  • Cosmetic-only treatments and over-the-counter moisturizers, coal-tar shampoos, and bath products
  • Routine treatments deemed not medically necessary, such as some spa or salt-room therapies
  • Drugs obtained outside an approved formulary without an exception—if your plan doesn’t list your biologic, you’ll need a formulary exception or appeal

Always confirm your specific biologic is on your Part D plan’s formulary during the Annual Enrollment Period, because formularies change yearly and a dropped drug can be costly.

Why Supplemental Coverage Is Decisive

Because psoriasis and psoriatic arthritis are chronic—often meaning decades of treatment—the coverage you choose compounds year after year.

  • Medigap Plan G pays your 20 percent Part B coinsurance with no annual limit, so even ongoing infliximab infusions leave you owing essentially only the small Part B deductible each year. Compare options in our Medigap plans guide.
  • Medicare Advantage caps your annual in-network out-of-pocket but adds prior authorization and step therapy—insurers frequently require you to try (and fail) a preferred biologic before approving another, and may steer you toward a specific administration route. Weigh the trade-offs in our Medicare Advantage vs. Original Medicare comparison and the cost-focused breakdown.

Because biologic decisions recur for life, locking in protection when your guaranteed-issue Medigap rights are active—rather than after a flare—is the smart financial move.

Help With Drug Costs

  • Extra Help (Low-Income Subsidy) sharply lowers Part D costs for those who qualify, making oral and self-injected biologics far more affordable.
  • Medicare Savings Programs can cover your Part B premium and, at the QMB level, your Part B coinsurance—directly relieving the uncapped infusion exposure. See our Medicare Savings Programs guide.
  • Manufacturer and foundation assistance can help with the $2,000 Part D cap, though the rules for combining them with Medicare differ from those for commercial insurance.

The Bottom Line

Medicare covers the full range of psoriasis and psoriatic arthritis care—dermatology and rheumatology visits, topicals, phototherapy, and the expensive biologics that control moderate-to-severe disease. The decisive financial fact is the infused-vs-self-injected split: self-injected and oral biologics under Part D are now capped at $2,000 a year, while infused biologics under Part B carry uncapped 20 percent coinsurance. Choosing the right supplemental coverage—ideally Medigap Plan G—and using Extra Help or Medicare Savings Programs where eligible turns a lifetime of biologic therapy into a predictable, affordable cost. For the bigger picture of budgeting for chronic conditions in later life, see our guide to healthcare costs in retirement.