Is Rebif (interferon beta-1a) covered by Medicare Part D?
311 of 5,052 Medicare Part D plan offerings (6.2%) list Rebif on their 2026 formulary, most often on tier 5; 70.8% of the formularies that cover it require prior authorization. Part D spending on it was $105 million in 2024 for 1,048 people: what plans and patients paid at the pharmacy, before manufacturer rebates (CMS Part D Spending by Drug).
- Plans that cover it
- 6.2%
- 311 of 5,052 offerings; the median drug: 76%
- Usual tier
- Tier 5
- from tier 1 to tier 5
- Prior authorization
- 70.8%
- of formularies that cover it; the median drug: 1%
- Quantity limits
- 50%
- of formularies that cover it; the median drug: 30%
8.3% of the formularies that cover it require step therapy (trying another drug first).
Source: CMS Part D formulary file, 2026 second quarter: the formularies in use in 2026. A plan's 2027 formulary can differ; check your own plan's coverage in Medicare Plan Finder.
What does it cost under Part D in 2027?
- Your yearly cap in 2027
- Out-of-pocket spending on covered Part D drugs stops at $2,400 in 2027 ($2,100 in 2026); after that, you pay nothing for covered drugs for the rest of the year.
- The deductible
- A plan's drug deductible is at most $700 in 2027 ($615 in 2026); many plans charge less or none.
Source: CMS, Announcement of calendar year 2027 Part D parameters; Medicare.gov, “How much does Medicare drug coverage cost?” (read Oct. 7, 2026).
How much does Medicare spend on it?
Part D spending by year
1,048 people filled it under Part D in 2024, in 9,289 claims. The amounts are what plans and patients paid at the pharmacy, before manufacturer rebates.
Source: CMS Medicare Part D Spending by Drug, 2020 to 2024 (published June 2026). Row used: Rebif (Interferon Beta-1a/Albumin).
Which forms and strengths are counted?
- 0.5 ml interferon beta-1a 0.044 mg/ml auto-injector
- 0.5 ml interferon beta-1a 0.044 mg/ml prefilled syringe
- 0.5 ml interferon beta-1a 0.088 mg/ml auto-injector
- 0.5 ml interferon beta-1a 0.088 mg/ml prefilled syringe
- pack of 6 × 0.2 ml interferon beta-1a 0.044 mg/ml auto-injector and 6 × 0.5 ml interferon beta-1a 0.044 mg/ml auto-injector
- pack of 6 × 0.2 ml interferon beta-1a 0.044 mg/ml prefilled syringe and 6 × 0.5 ml interferon beta-1a 0.044 mg/ml prefilled syringe
Which other versions are listed?
The same ingredients under other names, each with its own coverage and spending.
- Avonex (interferon beta-1a)20.1% of plan offerings
What else should you check?
- Stand-alone drug plans for 2027Premiums and deductibles
- Drugs Medicare spends the most onThe 2024 spending list
- 2027 costs and limitsDeductibles and out-of-pocket limits
Data, not medical advice. Coverage is the share of plan formularies listing the drug; your plan's formulary, tier and pharmacy decide what you pay.