Original Medicare denied a service as "not reasonable and necessary"? What the rule says and how to appeal.
Checked against the current rules on September 23, 2026.
A denial for a service as "not reasonable and necessary" isn't the end of the story — Original Medicare has 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
A service as "not reasonable and necessary" denials like this one turn on your own specific facts and documentation, not a single cited rule — the questions and evidence below are what actually decide it.
Questions that decide it
Before you appeal, these are the facts that usually decide whether a denial like this holds up:
Does the Medicare Summary Notice or the redetermination decision name a specific policy number (an NCD or LCD)?
Does your doctor's own documentation support that this service was medically necessary for your specific condition?
Was a less costly or more conservative treatment already tried and documented as insufficient before this service was ordered?
What a winning appeal has to show
An appeal that wins usually includes:
Chart notes, test results, or a letter from the treating physician addressing medical necessity — A denial for lack of medical necessity is won or lost on the specific clinical facts, not a general argument that care was needed. (Your doctor's office provides this.)
A specialist's consultation note, if one was involved in ordering the service — A specialist's own documented reasoning often carries more weight on a medical-necessity question than the referring provider's notes alone. (Your doctor's office provides this.)
Your deadline to appeal
120 days from the date on the Medicare Summary Notice — 120 calendar days from when you receive it (42 CFR § 405.942(a)), with receipt presumed to be 5 days after the notice's own date unless shown otherwise.42 CFR 405.942
Your Medicare contractor itself then has its own clock to decide. 60 calendar days from when the MAC receives your timely request. Each time you submit new evidence after filing, that 60-day clock is extended by up to 14 more calendar days for that submission (42 CFR § 405.950(a), (b)(3)) — this can happen more than once.
What to ask your doctor to address
If you're asking the treating physician for a supporting letter, it should speak to:
Whether the service was medically necessary for this patient's specific diagnosis, and why, addressing the specific policy criteria if one is named.
Why a less costly or more conservative alternative wasn't sufficient for this specific patient, if one was tried first.
Questions people ask
- Can your Medicare contractor 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 23, 2026
- 42 CFR 405.942as of September 23, 2026
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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.
