Medicare Part D denied a drug not on the plan's formulary? What the rule says and how to appeal.
Checked against the current rules on September 25, 2026.
A denial for a drug not on the plan's formulary isn't the end of the story — Medicare Part D plans have to follow specific coverage rules, and a denial that doesn't square with those rules is exactly the kind of appeal that tends to win.
Here's what the rule actually requires, what evidence usually turns a denial around, and the deadline you're working against.
What the rule requires
Coverage for a drug not on the plan's formulary under a Medicare Part D plan is governed by§ 423.578 Exceptions process. andFormulary Exceptions. A Medicare Part D plan generally cannot apply a stricter test than what these rules require.
Questions that decide it
Before you appeal, these are the facts that usually decide whether a denial like this holds up:
Has the patient already tried a formulary drug for this same condition that didn't work or caused a problem?
Has the prescriber already sent the plan a written statement about why the non-formulary drug is needed?
Did the plan's notice say the drug isn't on its formulary (drug list) at all, rather than citing a prior-authorization or step-therapy rule?
What a winning appeal has to show
An appeal that wins usually includes:
The prescriber's written supporting statement — §423.578(b) requires the plan to grant the exception once it determines the drug is medically necessary, consistent with the prescriber's own supporting statement — this is the single document the exception turns on. (Your doctor's office provides this.)42 CFR 423.578
Records showing formulary alternatives were tried, ineffective, or caused adverse effects — The exception standard is that formulary drugs for the condition would not be as effective or would have adverse effects for this patient — not simply that the prescriber prefers the requested drug. (Your doctor's office provides this.)42 CFR 423.578
The plan's own current formulary/drug list — Confirms the specific drug and tier status the denial is actually based on. (Request this from the plan.)CMS Guidance § 40.5.2
Your deadline to appeal
No deadline to make this first request — it's your initial ask, not yet an appeal. The 65-day appeal clock only starts once the plan denies it.42 CFR 423.566
The plan itself then has its own clock to decide. 72 hours for a standard drug-benefit request (24 hours if expedited). For an exception request, the clock instead runs from receipt of your prescriber's supporting statement — 72 hours standard / 24 hours expedited from that point, or from the end of a 14-day wait if the plan never receives one. Payment requests: 14 calendar days (42 CFR § 423.568, § 423.570, § 423.572).
What to ask your doctor to address
If you're asking the treating physician for a supporting letter, it should speak to:
The diagnosis and why this specific drug is needed for it.42 CFR 423.578
Which formulary alternatives were tried or considered, and why each would not be as effective or would cause adverse effects for this patient.42 CFR 423.578
Whether waiting for the standard timeframe could seriously jeopardize the patient's life, health, or ability to regain function (supports an expedited request).42 CFR 423.572
Questions people ask
- Can the plan just say it's "not medically necessary" with no further explanation?
- The denial notice has to explain the basis for the decision and tell you how to appeal. If it doesn't point to a specific rule or criteria, that's itself worth raising in your appeal — you're entitled to know what standard was applied.
- What if I don't have all the evidence listed above?
- Include what you have. An appeal with partial evidence and a clear explanation of the rule still gets a real review — it doesn't need to be complete to be worth filing.
Sources — last checked September 25, 2026
- § 423.578 Exceptions process.as of September 23, 2026
- 42 CFR 423.566as of September 23, 2026
- 42 CFR 423.572as of September 23, 2026
- CMS Guidance § 40.5.2as of July 6, 2026
- Formulary Exceptionsas of September 25, 2026
Related
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By CaseWhy Appeals editorial. See how this content is produced. Not legal advice. Not affiliated with or endorsed by Medicare, CMS, or any health plan. A product of CaseWhy LLC.
