Inflammatory bowel disease (IBD)—Crohn’s disease and ulcerative colitis—is a lifelong autoimmune condition, and while it’s often diagnosed in young adulthood, a large and growing share of patients are over 65 and managing it on Medicare. The modern treatment of IBD revolves around biologic drugs, which are extraordinarily effective and extraordinarily expensive. How Medicare pays for those biologics—and how much you owe—depends on one technical detail that catches many beneficiaries off guard: whether the drug is infused or self-injected. This guide walks through the entire path, from diagnosis to surgery, with a sharp focus on the drug-cost split that drives your out-of-pocket exposure.

Diagnosis and Monitoring Under Part B

The workup and ongoing monitoring of IBD are covered under Part B at 80 percent after the $257 deductible (2026), leaving you 20 percent coinsurance:

  • Gastroenterologist visits — 20 percent coinsurance
  • Colonoscopy and upper endoscopy with biopsy — when performed to diagnose or monitor disease (a diagnostic colonoscopy), 20 percent coinsurance applies. Note: a screening colonoscopy for colorectal cancer is free, but IBD patients usually need diagnostic and surveillance scopes, which carry cost-sharing. (If a screening colonoscopy turns therapeutic with a polyp removal, the coinsurance is reduced.)
  • CT and MR enterography to image the small bowel — 20 percent coinsurance
  • Lab monitoring — blood counts, inflammatory markers (CRP), and fecal calprotectin are covered as clinical laboratory tests, generally at no coinsurance
  • Therapeutic drug monitoring — measuring biologic drug levels and antibodies to guide dosing — covered under Part B

Because IBD requires lifelong surveillance—including regular colonoscopies due to the elevated colorectal cancer risk in long-standing colitis—these costs recur for life.

The Heart of IBD Cost: Infused vs. Self-Injected Biologics

Modern IBD is treated with biologics and targeted small molecules, and this is where Medicare’s coverage rules create dramatically different bills for what is medically similar treatment. The governing principle is the same one that runs throughout Medicare: how a drug is administered determines which part of Medicare pays. For the underlying framework, see Part B vs. Part D drugs.

Infused biologics → Part B (20%, no annual cap)

Biologics given by intravenous infusion in a clinic or hospital outpatient department fall under Part B, at 20 percent coinsurance with no annual out-of-pocket limit:

  • Infliximab (Remicade, and biosimilars Inflectra, Avsola, Renflexis) — IV every 8 weeks
  • Vedolizumab (Entyvio) — IV induction and maintenance
  • Ustekinumab (Stelara) — the IV induction dose is given as a Part B infusion

A maintenance infliximab infusion can carry a cost in the range of $3,000–$6,000+ per session depending on dose and biosimilar, so 20 percent coinsurance is roughly $600–$1,200 every eight weeks—potentially $4,000–$8,000 a year, every year, with no cap under Original Medicare without a supplement.

Self-injected and oral drugs → Part D (capped at $2,000)

Drugs you inject yourself at home or take by mouth fall under Part D, where your total out-of-pocket is capped at $2,000 for the year (2026):

  • Adalimumab (Humira, and biosimilars) — self-injected pen
  • Ustekinumab (Stelara) maintenance — self-injected (after the IV induction dose)
  • Risankizumab (Skyrizi), certolizumab (Cimzia), golimumab (Simponi) self-injected — Part D
  • Oral targeted small molecules — tofacitinib (Xeljanz) and upadacitinib (Rinvoq) JAK inhibitors, and ozanimod (Zeposia) — all Part D
  • Conventional maintenance drugs — mesalamine (Asacol, Lialda, Apriso), azathioprine, 6-mercaptopurine, methotrexate pills — inexpensive Part D generics

See Medicare Part D explained for how the $2,000 cap works.

The counterintuitive result

A patient on self-injected Humira or Skyrizi pays at most $2,000 for the entire year. A patient on infused Remicade or Entyvio can pay much more, because Part B has no cap. The drugs treat the same disease with similar effectiveness—but the route of administration, not the medicine, determines your bill. This is the most important financial fact in IBD coverage, and it means the choice between an infused and a self-injected biologic has real out-of-pocket consequences for someone on Original Medicare without a supplement.

This also means it’s worth discussing administration route with your gastroenterologist as a financial matter—where two options are clinically reasonable, a self-injected biologic under Part D may cost you far less than an infused one under Part B.

Why Medigap Plan G Erases the Infusion Exposure

Because infused biologics under Part B carry 20 percent coinsurance with no annual cap, the most important financial protection for an IBD patient on Original Medicare is a Medigap (Medicare Supplement) policy.

Plan G pays essentially all of the 20 percent Part B coinsurance after the small annual Part B deductible. For a patient on lifelong Remicade or Entyvio infusions, Plan G converts an open-ended $4,000–$8,000+ per year into a predictable monthly premium. See Medigap plans compared and the supplement vs. Advantage cost comparison.

As always, the catch is timing: Medigap is guaranteed-issue without medical underwriting only during your six-month open enrollment window at 65 (and certain special situations). An IBD diagnosis already on your record can make a later Medigap policy expensive or unavailable in most states—so this protection is best secured before you need it.

Medicare Advantage: Caps, but with Catches

A Medicare Advantage plan caps your in-network out-of-pocket each year (2026 maximum $9,250 in-network), which limits the uncapped Part B infusion exposure you’d face under Original Medicare without a supplement. But IBD care exposes the trade-offs sharply:

  • Prior authorization and step therapy — MA plans frequently require you to “fail” a cheaper drug before approving an expensive biologic, and may require prior authorization for each infusion
  • Networks — your gastroenterologist or specialized IBD center may be out of network
  • You still pay toward the out-of-pocket maximum every year

For patients on stable, expensive biologic regimens who value provider choice and the fewest treatment delays, Original Medicare plus Plan G is often preferable—provided Medigap was secured in time.

Flares, Steroids, and Surgery

Acute flares are managed with corticosteroids (prednisone, budesonide—inexpensive Part D drugs) and sometimes hospitalization. A severe flare requiring inpatient admission falls under Part A and its $1,676 (2026) deductible per benefit period, governed by the two-midnight rule.

When medication fails, surgery may be needed—bowel resection for Crohn’s, or colectomy with ileostomy or J-pouch for ulcerative colitis. Inpatient surgery falls under Part A, with surgeon fees under Part B at 20 percent coinsurance. Ostomy supplies are covered under Part B as durable medical equipment / prosthetic supplies at 20 percent coinsurance, and these are an ongoing, lifelong cost for patients with a permanent stoma.

Help for Lower-Income Beneficiaries

If your income and assets are limited:

  • Medicare Savings Programs can pay your Part B premium and, at the QMB level, your Part B coinsurance—erasing the 20 percent exposure on infused biologics. See Medicare Savings Programs.
  • Extra Help (Part D Low-Income Subsidy) brings self-injected biologic copays down to a few dollars.
  • Manufacturer patient assistance programs exist for most biologics, though some have restrictions for patients with Medicare drug coverage—a foundation grant is often the route for Medicare patients.

The Bottom Line

Medicare covers IBD comprehensively—diagnosis, monitoring, biologics, flares, and surgery—but your out-of-pocket cost hinges on how your biologic is delivered:

  • 20% with no cap — infused biologics (Remicade, Entyvio, Stelara IV induction) and other Part B services (the largest exposure)
  • Capped at $2,000/year — self-injected biologics (Humira, Skyrizi, Cimzia), oral JAK inhibitors, and conventional pills under Part D

The most important protective step is securing Medigap Plan G during your open enrollment window, before diagnosis—because it’s the uncapped Part B infusion coinsurance, not the Part D drugs, that creates the runaway bills. For how these recurring costs fit into a lifetime plan, see healthcare costs in retirement.