How to write a health insurance appeal letter
Reviewed by Main AI · Updated July 2026
A denial is not the last word — it is the start of a process you have a legal right to use. Many denials are reversed on appeal, especially when the letter pins down the plan’s own reason and answers it directly.
Start with the denial reason
Your denial letter or EOB states why the claim was denied — not medically necessary, out of network, missing prior authorization, a coding issue. Your appeal has to answer that specific reason, so read it closely before writing anything.
Internal appeal, then external review
Most plans require an internal appeal first — you ask the insurer to reconsider. If that fails, you generally have the right to an external review by an independent third party whose decision the insurer must honor. Both have deadlines, often measured from the date of the denial, so act promptly.
What to put in the letter
- Your identifiers: member ID, claim number, date of service.
- The denial reason: quote it from the letter or EOB.
- Your response: why the service is covered under your plan and, where relevant, medically necessary.
- Support: reference attached records — a letter of medical necessity from your provider carries real weight.
- The request: a formal appeal and a written decision, filed within the plan’s deadline.
Re: Member ID [id], Claim #[number], date of service [date]. "I am appealing the denial of the above claim, dated [date]. The stated reason was [quote the reason]. I believe this service is covered under my plan because [reason], and it was medically necessary as documented in the attached [records / provider letter]. I request a formal appeal and a written decision within the timeframe required by my plan." Attach the denial letter and supporting records.
If the internal appeal fails
Request an external review by an independent reviewer — under the Affordable Care Act, most plans must offer one, and the reviewer’s decision binds the insurer. Ask your provider’s office to help; they appeal denials routinely and can supply the clinical language that decides medical-necessity cases. Track every deadline, because missing one can end the appeal regardless of the merits.
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Analyze your document — freeCommon questions
What is the difference between an internal and external appeal?
An internal appeal asks the insurer to reconsider its own decision. An external review sends it to an independent third party whose decision the insurer must follow. You usually must do the internal appeal first.
How long do I have to appeal?
Deadlines are set by your plan and are often measured from the denial date. They can be tight, so start as soon as you get the denial and confirm the exact window in your plan documents.
What does "medically necessary" mean?
That the service is appropriate and needed to diagnose or treat your condition under accepted standards. A letter of medical necessity from your provider is the strongest way to establish it.
What if my internal appeal is denied?
You generally have the right to an external review by an independent body. Under the ACA, most plans must offer one, and its decision is binding on the insurer.
Can my doctor help with the appeal?
Yes, and it helps a lot. Provider offices appeal denials routinely and can supply the clinical documentation and language that decide medical-necessity cases.