How to Appeal a Health Insurance Denial

A health insurance denial doesn't have to be the final word. Whether your claim was rejected for a missing prior authorization, a coverage dispute, or a vague "not medically necessary" determination, you have formal rights to challenge that decision — and insurers are required by federal law to give you a meaningful opportunity to appeal. The process is more structured than most people realize, and knowing how to work it step by step can make the difference between a $40,000 bill and a $0 balance.

What does "insurance denied my claim" actually mean?

Insurance companies issue two types of unfavorable decisions, and the terminology matters for how you respond. A denial occurs after a service has been provided — the insurer reviewed the claim and refused to pay. A denial of prior authorization (also called a preauthorization denial or adverse determination) happens before or during care — the insurer refuses to approve a service in advance. Both are appealable, but the timelines and urgency levels differ.

Your denial will arrive in a document called an Explanation of Benefits (EOB) or, for prior authorization denials, a written adverse determination notice. Federal law under the Affordable Care Act requires insurers to include in this notice:

• The specific reason for the denial
• The clinical criteria or plan provisions used to make the decision
• Instructions for how to file an internal appeal
• Information about your right to external review

Read this document carefully. The denial code and stated reason are the foundation of your entire appeal strategy. A denial for "not medically necessary" requires different evidence than one for "out-of-network provider" or "missing prior authorization."

What are my legal rights when an insurance claim is denied?

Under the Affordable Care Act, most health plans — including employer-sponsored plans governed by ERISA and individual marketplace plans — must provide a two-stage appeals process: an internal appeal followed by an independent external review. Grandfathered plans and some self-funded plans may have different rules, so confirm which framework applies to your policy.

Key federal protections include:

• Internal appeal deadlines: For urgent/concurrent care denials, insurers must respond within 72 hours. For pre-service denials, within 30 days. For post-service (retrospective) claims, within 60 days.
• External review: After exhausting internal appeals, you can request an independent review by a certified Independent Review Organization (IRO). The IRO's decision is binding on the insurer.
• Expedited appeals: If your health or ability to function is at serious risk, you can request an expedited internal appeal — the insurer must respond within 72 hours.
• Continued coverage during appeals: If a claim is denied while you are in the middle of ongoing treatment, you may have the right to request continuation of coverage during the appeal period.

Your state may provide additional protections on top of these federal minimums. State insurance commissioners can be valuable allies — more on that below.

How do I file an internal appeal with my insurance company?

The internal appeal is your first formal step, and it sets the record for everything that follows. Do not treat it as a phone call or informal complaint. Here is how to build a strong appeal:

1. Get the specific denial reason in writing. If you received only a phone call, request a written adverse determination notice before doing anything else.
2. Request the insurer's clinical criteria. You have the right to receive the specific guideline or criteria — such as InterQual or MCG (formerly Milliman Care Guidelines) criteria — used to deny your claim. Ask for it explicitly in writing.
3. Obtain your medical records. You can request your records at any time. The provider must respond within 30 days (with a possible 30-day extension). Look for documentation that directly supports medical necessity: physician notes, test results, imaging reports, specialist referrals, and treatment histories.
4. Get a Letter of Medical Necessity from your doctor. This is critical. The letter should directly address the insurer's stated denial reason, cite the clinical criteria the insurer used, and explain why your situation meets — or why those criteria are inappropriate for — your condition.
5. Research the diagnosis and procedure codes. Confirm that the codes on the claim (ICD-10 for diagnosis, CPT for procedure) are accurate and align with your medical records. Coding errors are among the most common and most easily corrected denial causes.
6. Submit everything in writing. Send your appeal by certified mail or through the insurer's secure portal with a documented submission timestamp. Keep copies of every document you send.
7. Track your deadline. Most plans require internal appeals to be filed within 180 days of receiving the denial. Check your EOB or plan documents for the exact window — missing it can forfeit your rights.

What if my internal appeal is denied — can I get an independent review?

Yes. If your internal appeal is upheld (meaning the insurer still refuses to pay), you have the right to request an External Review by an independent organization with no financial relationship to your insurer. For most ACA-compliant plans, this process is governed by federal rules administered through your state's insurance department or, for self-funded ERISA plans, through a federally-facilitated process.

To initiate external review:

1. Request external review within 4 months of receiving the final internal denial (the exact deadline varies by state — verify with your state insurance department).
2. Complete the external review request form provided by your insurer or your state insurance department. Many states have these forms available online.
3. Submit the same supporting documentation you used in your internal appeal, plus the insurer's final denial letter.
4. An Independent Review Organization will assign a clinical reviewer — typically a board-certified specialist in the relevant field — who will evaluate the case.
5. The IRO must issue a decision within 45 days for standard reviews and within 72 hours for expedited reviews. If the IRO rules in your favor, the insurer is legally required to cover the service.

External review overturns insurer denials in a meaningful number of cases — particularly for medical necessity disputes where a clinical expert can counter the insurer's in-house reviewers with peer-reviewed evidence.

When should I contact my state insurance commissioner?

Your state's Department of Insurance (DOI) is an underutilized resource that costs you nothing to use. You can — and often should — file a complaint with your state insurance commissioner in parallel with your internal appeal. This is not the same as requesting external review; it is a regulatory complaint that puts the insurer on notice that a state authority is watching.

Contact your state DOI if:

• The insurer misses its required response deadlines
• You believe the denial violates state insurance law (for example, mental health parity laws requiring equal coverage for behavioral health services)
• The insurer's explanation is vague, contradictory, or fails to cite specific clinical criteria
• You are experiencing a simultaneous billing or collections pressure that feels premature

For employer-sponsored self-funded plans (common at large employers), the state DOI has limited jurisdiction — those plans are regulated federally under ERISA. In that case, the U.S. Department of Labor's Employee Benefits Security Administration (EBSA) is your federal contact. You can reach EBSA at dol.gov/agencies/ebsa.

How do I appeal a "not medically necessary" denial specifically?

Medical necessity denials are the most common — and the most winnable — type of insurance appeal. Insurers use third-party clinical criteria to make these determinations, and those criteria are not always current with emerging evidence or individual patient circumstances. A strong counter-argument focuses on three things:

• Peer-reviewed evidence: Published clinical studies, guidelines from professional medical associations (such as ACOG for obstetric care, or AAP for pediatric care), and systematic reviews that support the recommended treatment.
• Your specific clinical history: Demonstrate that you have tried and failed alternative treatments the insurer might claim are sufficient, or that those alternatives are contraindicated for your specific condition.
• A specialist's opinion: A letter from a specialist — ideally board-certified in the relevant field — carries more weight than a primary care statement alone. If possible, have the physician speak directly to the insurer's specific denial rationale.

Request a peer-to-peer review: your physician can request a direct phone call with the insurer's medical director who issued the denial. This is an informal but often effective step that happens before or alongside the formal appeal, and many denials are reversed at this stage without the patient needing to file a written appeal at all.