A “not medically necessary” denial means your plan agrees the service is covered in general but says it was not appropriate for your situation. This letter pushes back by tying your care to the plan’s own definition of medical necessity and to recognized clinical guidelines, backed by your treating provider’s judgment. Under the Affordable Care Act, non-grandfathered plans generally allow at least 180 days from the date of the denial to file an internal appeal — but the controlling deadline is on your own denial letter, so check it first.
Before you appeal
- The denial letter or EOB with the exact reason and any code.
- Your provider’s letter of medical necessity (diagnosis, what was tried, why this service is needed, expected outcome).
- The clinical records that support the request: notes, test results, imaging, prior treatment history.
- The clinical guidelines you rely on (for example, specialty-society or recognized national guidelines).
- The plan’s medical-necessity definition from your plan documents (Summary Plan Description or Evidence of Coverage).
- The specific criteria the plan used — you can request these in writing (see the claim-file request below).
The letter
[Your full name]
[Your address]
[City, State ZIP]
[Phone] | [Email]
[Date]
[Insurance company - Appeals Department]
[Address from your denial letter]
Re: Internal appeal of "not medically necessary" denial
Member: [Name] Member ID: [number] Group #: [number]
Claim number: [number] Date(s) of service: [dates]
Denial date: [date] Denial reason/code: [as stated on the denial letter/EOB]
To the Appeals Department:
I am appealing the denial of the service above, which was denied as not
medically necessary. I ask the plan to overturn this decision and approve
coverage.
This service is medically necessary for my condition. My treating provider,
[provider name and specialty], has determined that [service/treatment] is
appropriate to treat [diagnosis]. The enclosed letter of medical necessity
explains the clinical reasoning, the treatments already tried, and why this
service is needed now.
This request meets the plan's own definition of medical necessity and is
consistent with recognized clinical guidelines for [condition], including
[name the guideline or specialty society if known]. The denial does not
appear to account for [the specific clinical facts in my records / the
treatments I have already tried / my provider's assessment].
So that I can respond fully, please provide in writing the specific
medical-necessity criteria, clinical guidelines, and any internal rules the
plan used to make this decision, and the credentials of the reviewer.
I also request a peer-to-peer review between my treating provider and the
plan's reviewing physician of the same or similar specialty.
Enclosed in support:
- Copy of the denial letter / EOB
- Letter of medical necessity from [provider name]
- Relevant clinical records and test results
- Relevant clinical guideline excerpts (if available)
Please send me a written decision by the plan's required timeframe. If the
denial is upheld, please send the information I need to request an external
(independent) review.
Thank you,
[Your signature]
[Your printed name]
How to send it
File within your plan’s appeal deadline — the date is on your denial letter (ACA plans generally allow at least 180 days). Use certified mail with return receipt, or your plan’s official appeals channel (fax, portal, or member-services address), and keep a dated copy of everything you send. If a delay could seriously jeopardize your health, ask for an expedited appeal and a peer-to-peer review so the plan’s reviewing physician talks directly with your provider.
Notes. Under the ACA internal-claims and appeals rules (29 CFR 2590.715-2719), non-grandfathered plans must give you at least 180 days from notice of an adverse benefit determination to file an internal appeal, and must provide, on request and free of charge, the criteria and evidence used to decide your claim. Many medical-necessity denials are overturned at the external review stage, so do not stop after one internal appeal. See also request your claim file (ERISA), request a peer-to-peer review, and the internal appeal letter. This is general information, not legal or medical advice.