Part B vs Part D drugs: which part pays for your medication?
How Medicare decides whether a drug is covered under Part B (given in a doctor's office or with equipment) or Part D (picked up at a pharmacy), and the cost differences.
Most prescriptions you pick up at a pharmacy fall under Part D. But some drugs are covered by Part B, with different costs.
| Drug situation | Usually covered by | Your cost in Original Medicare |
|---|---|---|
| Infusion or injection given in a doctor's office | Part B | 20% after Part B deductible |
| Chemotherapy (IV and some oral) | Part B | 20% |
| Insulin used in a traditional pump | Part B | Capped at $35/month |
| Insulin injected with pens or syringes | Part D | Capped at $35/month |
| Flu, pneumonia, hepatitis B shots | Part B | $0 for flu and pneumonia |
| Shingles and most other vaccines | Part D | $0 for recommended vaccines |
| Pills picked up at a pharmacy | Part D | Plan copays, $2,100 yearly cap |
Why it matters
Part B drug coinsurance has no annual cap in Original Medicare. Expensive infusions can cost thousands. Medigap plans cover that 20%; see Plan G vs Plan N.
Part D has a yearly $2,100 cap in 2026; see how the cap works.
Part B drug coinsurance relief
For some Part B drugs whose prices rose faster than inflation, Medicare lowers coinsurance each quarter. Ask your provider.
Questions people ask
Is insulin Part B or Part D?
Part B if used in a traditional pump; Part D otherwise. Both capped at $35 a month.
Are infusions Part B?
Usually, when given in a doctor's office or clinic.
Does Part B have a drug cost cap?
No, in Original Medicare. Medigap can cover the 20%.
Which vaccines are Part B?
Flu, pneumonia, hepatitis B for some, and COVID-19.
Independent educational site. Not affiliated with or endorsed by the U.S. government, the federal Medicare program, or any insurance company. Figures are 2026 amounts published by CMS unless noted; check Medicare.gov for your situation.