Will all Medicare drug plans cover formulary insulin for only $35 per month (or less)?

Yes. The Inflation Reduction Act (IRA) requires that a 30-day supply of any insulin product on a Medicare Part D prescriptions drug plan's formulary is covered at a maximum $35 copay through the Initial Deductible (if any) and the Initial Coverage phase.

As a practical note, many Medicare Part D drug plans will offer some formulary insulin products for a copay of less than $35 (for example, a $20 copay for a one-month supply).

If you have higher out-of pocket expenses (over $2,100), and exit the 2026 Initial Coverage phase, you will have no additional costs for any formulary drugs (including insulin) for the remainder of the year.

As a reminder, the IRA eliminated beneficiary cost-sharing during the Catastrophic Coverage phase in 2024 and beginning with plan year 2025, the IRA eliminated the Coverage Gap (Donut Hole) as the third phase of Part D drug coverage and a Part D beneficiary does not have any additional expenses for formulary drugs after reaching the Part D maximum out-of-pocket threshold (RxMOOP) of $2,100 in 2026.

As a note, since June 2023, insulin furnished through Medicare Part B durable medical equipment (DME) coverage (such as used in insulin pumps) will also have a monthly copay of no more than $35.

Finally, starting in 2026, the United States government can begin negotiating drug prices directly with pharmaceutical companies, so the future copay for insulin may be less than $35 depending on the government's negotiated price. A bit of history:

The IRA's $35 insulin copay is similar to the 2021-2022 Senior Savings Model coverage. However, unlike the earlier Senior Saving Model, the Inflation Reduction Act of 2022 expands the insulin $35 copay to all Medicare Part D prescription drug plans or Medicare Advantage plans offering prescription drug coverage (MAPDs) and includes all Part D forms of insulin found on a drug plan's formulary or drug list.

Sources include:

https://www.cms.gov/newsroom/press-releases/cms-launches-groundbreaking-model-lower-out-pocket-expenses-insulin
https://www.cms.gov/newsroom/fact-sheets/part-d-senior-savings-model
https://innovation.cms.gov/files/x/partd-seniorsav-plan-rfa.pdf
https://innovation.cms.gov/innovation-models/part-d-savings-model
https://www.cms.gov/newsroom/press-releases/trump-administration-continues-keep-out-pocket-drug-costs-low-seniors
https://innovation.cms.gov/media/document/partd-seniorsav-cy21-spraddendum
https://innovation.cms.gov/media/document/partd-senior-savings-model-cy21-faqs