How to Write an Insurance Appeal Letter That Gets Results

Not every denied claim requires a formal appeal — some are simple errors that a phone call can fix. But you should file a written appeal whenever:

• —Your insurer denies coverage for a service your doctor ordered, citing it as "not medically necessary"
• —A claim is denied because the insurer says the service is "experimental" or "investigational"
• —You are told the service requires prior authorization that was not obtained, but you believe it was or that it should not have been required
• —An emergency claim is denied on the grounds that it was not a true emergency
• —The insurer applies out-of-network cost-sharing to a provider you believed was in-network
• —Your claim is denied due to a coding error that the provider's office cannot or will not correct

The key principle: if you received care that your doctor deemed necessary, and your plan covers that type of care, you should appeal. Insurers deny claims for administrative and financial reasons that often have nothing to do with whether the care was appropriate ².

Federal law guarantees you two levels of appeal for denied claims ³.

Internal appeal — your first step. You submit your appeal directly to your insurance company, and a different reviewer (someone who was not involved in the original denial) evaluates your case. The insurer must complete their review within:

• —30 days for non-urgent pre-service denials
• —60 days for post-service denials (care already received)
• —72 hours for urgent/concurrent care denials

If the internal appeal is denied, you then have the right to an external review. This is conducted by an independent third party that has no affiliation with your insurance company. The external reviewer's decision is binding on the insurer — if they rule in your favor, the insurer must pay the claim.

External review is remarkably effective. Studies show that external reviewers overturn insurer denials in 40-60% of cases ¹, depending on the state and type of service. The external review process is free to the patient.

Important: You typically must exhaust the internal appeal before requesting external review. However, if your situation is urgent — for example, a denial of ongoing cancer treatment — you can request an expedited external review simultaneously with your internal appeal.

An effective appeal letter is structured, specific, and evidence-based. Every appeal letter should contain these elements:

1. Header information:

• —Your name, policy number, and group number
• —The claim number and date of service
• —The date of the denial and the denial reference number

2. Clear statement of purpose:

• —State explicitly that you are filing a formal appeal of the denied claim
• —Reference the specific reason for denial from the EOB or denial letter

3. Why the denial is wrong:

• —Address the insurer's stated reason for denial directly
• —If the denial cites medical necessity, include your doctor's explanation of why the service was necessary
• —If the denial cites network status, provide evidence that the provider was in-network or that no in-network alternative was available
• —If the denial cites coding issues, include corrected codes from your provider

4. Supporting evidence:

• —A letter from your treating physician explaining the medical necessity
• —Relevant medical records and test results
• —Published clinical guidelines or peer-reviewed studies supporting the treatment
• —Your plan's own coverage documents showing that the service is covered

5. Specific request:

• —State exactly what you want: full payment of the claim at in-network rates, reconsideration of the medical necessity determination, etc.

6. Deadline reference:

• —Note the regulatory deadline for the insurer's response

Use this framework to organize your appeal letter. Adapt the language to your specific situation.

Opening paragraph: "I am writing to formally appeal the denial of claim [claim number] for [service description] performed on [date of service]. The denial, dated [denial date], states that [quote the denial reason]. I believe this denial is incorrect for the reasons detailed below, and I request that [Insurance Company] reverse the denial and process the claim for payment."

Medical necessity paragraph (if applicable): "My treating physician, Dr. [Name], determined that [service] was medically necessary to [diagnose/treat] my condition. [Explain the clinical reasoning — what symptoms or test results led to the decision, what alternatives were considered, and why this specific service was required.] Dr. [Name]'s supporting letter is attached."

Coverage paragraph: "My plan's Summary of Benefits and Coverage confirms that [service type] is a covered benefit under my plan. [Reference the specific section or page of your plan documents.] The denial reason of [reason] does not align with my plan's coverage terms because [explain]."

Evidence paragraph: "In support of this appeal, I am including the following documentation: [numbered list of all attachments — physician letter, medical records, clinical guidelines, plan documents, etc.]"

Closing paragraph: "I respectfully request that [Insurance Company] reverse this denial and process claim [number] for full payment within the [30/60]-day regulatory timeframe. If this internal appeal is denied, I intend to exercise my right to an independent external review. Please confirm receipt of this appeal in writing."

The strength of your appeal is directly proportional to the quality of your supporting evidence. Here is how to gather what you need:

From your doctor:

• —Request a letter of medical necessity — this is the single most important document in your appeal. Ask your doctor to explain, in clinical terms, why the service was necessary for your specific condition. The letter should reference your diagnosis, symptoms, prior treatments attempted, and why the denied service was the appropriate next step.
• —Request copies of relevant medical records — office visit notes, test results, imaging reports, and any documentation that supports the treatment decision.

From your insurer:

• —Request the complete clinical criteria used to deny your claim. Insurers often use proprietary medical necessity guidelines (such as InterQual or MCG). You have the right to see the specific criteria applied to your case.
• —Request your full plan documents — not just the Summary of Benefits, but the complete Evidence of Coverage or Certificate of Insurance. The detailed plan documents often contain coverage provisions that the summary omits.

From clinical literature:

• —If your insurer claims a treatment is experimental or not medically necessary, find published clinical guidelines from relevant medical societies (e.g., American College of Cardiology, American Cancer Society) that recommend the treatment for your condition.

From your bill data:

• —Upload your bill to ORVO to document the fair market cost of the service. If your appeal involves out-of-network cost-sharing disputes, showing that the provider's charges are within the normal range for your area strengthens your position.

Missing a deadline can forfeit your appeal rights. Know these timelines and calendar them immediately:

Your deadlines:

• —Internal appeal: Most plans require you to file within 180 days of receiving the denial. Some plans allow less. Check your denial letter for the specific deadline.
• —External review: You typically have 4 months (or 60 days in some states) after the internal appeal denial to request external review.
• —Urgent appeals: If the denial involves ongoing treatment or a condition that could seriously jeopardize your health, you can request an expedited review — the insurer must respond within 72 hours ³.

Insurer deadlines:

• —30 days to respond to a pre-service internal appeal
• —60 days to respond to a post-service internal appeal
• —72 hours for urgent care appeals
• —45 days for external review decisions (varies by state)

What to do if the insurer misses their deadline: If the insurer does not respond within the regulatory timeframe, this is itself a violation. Contact your state insurance commissioner to report it. In some states, a missed deadline results in automatic approval of the appeal.

If both your internal appeal and external review are denied — or if your insurer is not following proper procedures — you have additional escalation paths.

State insurance commissioner:

• —Every state has an insurance department that oversees health insurers and investigates consumer complaints. Filing a complaint is free and can be done online in most states.
• —The commissioner can investigate whether your insurer followed proper claims processing and appeal procedures, and can intervene directly on your behalf.
• —Insurers take commissioner complaints seriously because they can trigger audits and enforcement actions.

Additional escalation options:

• —Contact your employer's HR department (for employer-sponsored plans). Employers are the insurer's client and have leverage that individual patients do not.
• —File a complaint with CMS if you have a marketplace (ACA) plan or Medicare Advantage plan.
• —Contact your state attorney general if you believe the insurer's denial constitutes bad faith or unfair business practices.
• —Seek legal counsel for large-dollar denials (surgery, extended hospitalization, specialized treatments). Many attorneys who specialize in insurance denial cases work on contingency, meaning you pay nothing unless they win.
• —Contact your elected representatives — congressional offices have constituent services departments that can make inquiries to federal agencies on your behalf.

The appeals process is designed to resolve most disputes. But when it fails, regulatory and legal pressure often succeeds where administrative processes do not.