An “experimental” or “investigational” denial says the plan does not consider your treatment proven enough to cover. This letter counters that label with peer-reviewed published evidence, recognized treatment guidelines, FDA approval or clearance status, and the plan’s own definition of “experimental.” Under the Affordable Care Act, non-grandfathered plans generally allow at least 180 days from 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 code, and the plan’s “experimental” definition.
- Your treating provider’s supporting letter explaining why this treatment is appropriate for you.
- Peer-reviewed published studies supporting the treatment for your condition.
- Recognized treatment guidelines (for example, specialty-society or national guidelines).
- The treatment’s FDA approval or clearance status, if applicable.
- The plan’s specific criteria for calling something experimental — request these in writing if needed.
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 "experimental / investigational" 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 [treatment/service], which was denied as
experimental or investigational. I ask the plan to overturn this decision and
approve coverage.
This treatment is not experimental for my condition. My treating provider,
[provider name and specialty], has determined it is appropriate to treat
[diagnosis]. The denial does not reflect the current published evidence or
the plan's own definition of "experimental."
In support, I point to the following [keep what applies]:
- Peer-reviewed published studies showing this treatment is effective and
accepted for [condition]: [cite or enclose].
- Recognized treatment guidelines that include this treatment for my
condition: [name the guideline or specialty society].
- The treatment's FDA approval or clearance status: [describe, if
applicable].
- The plan's own definition of "experimental," which this treatment does not
meet given the evidence above.
So that I can respond fully, please send me in writing the specific criteria,
guidelines, and evidence the plan used to classify this treatment as
experimental, and the credentials of the reviewer.
Enclosed in support:
- Copy of the denial letter / EOB
- Supporting letter from [provider name]
- Peer-reviewed studies and guideline excerpts
- FDA status documentation (if applicable)
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. If a delay could seriously jeopardize your health, ask for an expedited appeal. Many experimental/investigational denials are overturned at the external-review stage, so be ready to escalate if the internal appeal is upheld.
Notes. Under the ACA internal-claims and appeals rules (29 CFR 2590.715-2719), plans must give you at least 180 days to appeal and must provide, on request, the criteria and evidence used to decide your claim. Experimental/investigational and medical-necessity denials are among those most frequently reversed by an independent review organization (IRO) on external review, which is binding on ACA plans. See also appeal a ‘not medically necessary’ denial and request your claim file (ERISA). This is general information, not legal or medical advice.