- Most self-administered arthritis biologics fall under Part D, while biologics infused in a clinic generally fall under Part B.
- Biologics usually sit on the specialty tier, where coinsurance applies, but 2026 out-of-pocket spending on covered Part D drugs is capped at $2,100.
- Check your exact drug, tier, pharmacy, and restrictions before enrolling, and ask about biosimilars, exceptions, and appeals if coverage is denied.
If you take a biologic drug for arthritis, will Medicare Part D cover it — and what will you actually pay? For rheumatoid arthritis, psoriatic arthritis, or ankylosing spondylitis, the answer starts with how the drug is given — which decides Part D vs. Part B — and then your plan's tier.
Part D or Part B? How the drug is given decides
Medicare does not sort arthritis drugs by diagnosis alone. As a general rule, Part D covers drugs you take yourself, including most self-injected biologics and oral targeted therapies taken at home, when they are on your plan's formulary. Part B generally covers drugs administered in a doctor's office, clinic, or hospital outpatient setting, such as infused biologics.
Some drugs come in more than one form, so confirm which part covers your specific prescription and setting.
Why biologics land on the specialty tier
Part D plans organize covered drugs into tiers. Lower tiers usually carry flat copayments; the specialty tier, typically the highest, is reserved for high-cost drugs needing special handling, storage, or monitoring — where most biologics sit.
On the specialty tier, cost-sharing is usually coinsurance, a percentage of the drug's cost, rather than a fixed copayment. That means your pharmacy bill can be large early in the year, even if your yearly total is capped. Plans may also require a designated specialty pharmacy, which often ships the drug to your home or doctor's office.
Two other plan tools commonly apply to biologics: prior authorization, where your prescriber must confirm the drug is medically necessary, and step therapy, where the plan asks you to try a preferred drug first unless your prescriber documents why it would not work as well or could cause harm.
Neither tool means a drug is uncovered — but check the rules before your first fill, not after you run out.
What you pay in 2026
In 2026, the standard Part D structure works like this:
- The maximum standard deductible is $615. Some plans charge less, or $0 for certain tiers.
- After the deductible, you generally pay a copayment or coinsurance until your out-of-pocket spending on covered drugs reaches $2,100.
- Once you reach $2,100, you pay $0 for covered Part D drugs for the rest of the calendar year.
- The "donut hole" coverage gap was eliminated in 2025, so there is no separate gap phase.
- Your monthly premium, and drugs your plan does not cover, do not count toward the $2,100 cap.
Because biologics are expensive, many people taking them reach the cap early in the year. The Medicare Prescription Payment Plan can help by spreading out-of-pocket costs across monthly payments — it does not lower your total, but it can smooth a large early bill. People with limited income may also qualify for Extra Help, which lowers premiums, deductibles, and copayments.
Biosimilars: a lower-cost option to ask about
A biosimilar is highly similar to an original biologic, with no clinically meaningful differences in safety or effectiveness for its approved uses. Biosimilars are not generics — biologics are made from living cells, so an exact copy is not possible — but they are often priced lower.
If your plan lists a biosimilar version of your biologic, ask your prescriber and pharmacist about it. Switching is a medical decision, not just a cost decision: weigh how well your current treatment works and your injection device or administration method. A plan may prefer a biosimilar, so check which version it covers and at what tier.
How to check your biologic before you enroll or refill
Before enrollment or a refill, work through this checklist:
- Search your plan's formulary for your exact drug, dose, and form.
- Note the tier and whether cost-sharing is a copayment or coinsurance.
- Check for restrictions such as prior authorization, step therapy, or a quantity limit.
- Confirm the pharmacy — many specialty drugs must go through a designated specialty pharmacy.
- Compare plans on Medicare Plan Finder using your full medication list during the Annual Enrollment Period, October 15 through December 7.
- Read your Annual Notice of Change each fall, because tier and restrictions can change year to year.
If a new plan does not cover a drug you were taking, ask about a transition fill — a temporary supply while you pursue an exception or alternative.
If your biologic is denied or restricted
A denial is not necessarily the end of the story. You or your prescriber can request a coverage determination, including a formulary exception asking the plan to cover the drug or waive a restriction, usually with a supporting statement explaining why preferred alternatives would not work as well or could cause harm.
If the exception is denied, you can appeal, starting with a redetermination by the plan. Keep copies of every letter, note the date of every call, and start promptly. Free help is also available from your State Health Insurance Assistance Program (SHIP). This article is educational only, not medical or insurance advice.
Bottom line: Most self-administered arthritis biologics fall under Part D on the specialty tier, where coinsurance can be steep early in the year but 2026 out-of-pocket costs on covered drugs are capped at $2,100 — so check your exact drug, tier, and pharmacy before enrolling, ask about biosimilars, and appeal promptly if coverage is denied.