How to Appeal a Denied Health Insurance Claim and Actually Win

Fact-checked by the Smart Insurance 101 editorial team

What do you do when you follow every rule, get the care your doctor ordered, and then receive a letter saying your insurer won’t pay? Learning to appeal a denied health insurance claim is the single most important skill a policyholder can have, and most people never use it. According to KFF’s 2024 analysis of HealthCare.gov marketplace plans, insurers denied 19% of in-network claims submitted that year, yet fewer than 1% of those denials were ever challenged by consumers.

That gap matters. Insurers are not infallible, and the appeals process exists precisely because Congress recognized that. This guide walks through every stage, from reading the denial letter correctly to escalating to an independent reviewer, so you know exactly what to do and when.

Why Your Claim Was Denied and What the Letter Actually Means

The denial letter is not a final verdict. Read it as a diagnosis: it tells you exactly what argument you need to counter. Most denial reasons fall into a handful of categories, and knowing which one you are dealing with determines your next move.

Decoding the Most Common Denial Reasons

“Not medically necessary” is the most frequent and most contestable denial code. It means a clinical reviewer at the insurer decided the care did not meet the plan’s coverage criteria, not that your doctor was wrong. That distinction matters, because a strong rebuttal from your physician, backed by clinical guidelines, can change the outcome. Other common codes include “prior authorization not obtained,” “service not covered,” and “out-of-network provider.” Each requires a different fix.

Billing and coding errors form their own category, and they are frequently overlooked. If the denial stems from a mismatched procedure code or an incorrect diagnosis code, the solution often lives in your provider’s billing department, not with you filing a formal appeal. Call the provider first, ask them to verify the codes submitted, and request a corrected claim resubmission if an error is found. This can resolve a denial in days without ever touching the formal appeals process. Understanding how deductibles and out-of-pocket costs interact with claim payments is also worth reviewing; our breakdown of health insurance deductibles vs. out-of-pocket maximums can clarify what you actually owe after a denial is resolved.

Pre-Service vs. Post-Service Denials

A pre-service denial blocks a requested prior authorization before care happens. A post-service denial rejects a claim after you have already received treatment. The distinction shapes your urgency: a pre-service denial may mean you cannot get the care at all without paying out of pocket, while a post-service denial means a bill is already sitting somewhere waiting. Both are appealable, but expedited timelines apply differently, which is covered in a later section.

Your Legal Rights and Strict Timelines for Appeals

Federal law gives you a clearly defined window to fight a denial, and missing those deadlines can forfeit your rights entirely. The Affordable Care Act requires insurers to provide a written explanation of every denial and to allow an internal appeal within 180 days of receiving the denial notice, as outlined by the U.S. Department of Labor’s ERISA claims guidance.

ACA Plans vs. Self-Funded ERISA Plans

Not all plans follow the same rules. If your insurance comes through a large employer that self-funds its health plan rather than purchasing coverage from an insurer such as UnitedHealthcare, Anthem, or Aetna, that plan is governed by ERISA (the Employee Retirement Income Security Act) and is generally exempt from state insurance laws. This means state-mandated external review rights may not apply. You still have federal internal appeal rights under ERISA, but your escalation path after an internal denial runs through the U.S. Department of Labor or federal court, not your state insurance commissioner. Check your Summary Plan Description to determine whether your employer’s plan is self-funded.

Fully insured plans purchased through the ACA marketplace or directly from an insurer are subject to both federal ACA rules and state law. The Nebraska Department of Insurance’s appeals guidance illustrates how state law layers on top of the federal baseline, requiring a formal two-stage process: internal review first, then external review by an independent organization. Major insurers operating on the exchanges, including Blue Cross Blue Shield, Cigna, and Humana, are bound by this framework in states where they offer fully insured products.

Expedited Rights and Continued Coverage

For situations involving urgent care, the standard timelines compress significantly. Insurers must respond to an expedited internal appeal within 72 hours, according to the National Association of Insurance Commissioners (NAIC). Separately, if you are in the middle of an ongoing course of treatment and your insurer decides to discontinue coverage for it, you generally have the right to continue receiving that care while the appeal is pending.

Building a Strong Internal Appeal with Evidence That Works

A winning internal appeal addresses the insurer’s exact stated reason, point by point, with clinical evidence. A generic letter asking the insurer to “reconsider” almost never works. Here is what actually moves the needle.

The Letter of Medical Necessity Is the Core Document

Ask your doctor to write a letter of medical necessity that is specific, not generic. The letter should name the patient’s diagnosis, describe what treatments were already tried and why they failed or were contraindicated, cite published clinical guidelines (such as those from the American College of Physicians, the American Heart Association, or condition-specific specialty societies), and explain directly why the denied service meets the insurer’s own coverage criteria. A letter that says “this treatment is necessary for my patient’s care” does almost nothing. A letter that says “per the 2024 AHA guidelines, Class III heart failure warrants this intervention after documented failure of two prior therapies, both of which this patient has completed” gives a reviewer something to work with.

Your appeal package should also include: the original Explanation of Benefits (EOB) showing the denial, any prior authorization correspondence, relevant office notes and lab results, and the specific plan language that you believe supports coverage. The Texas Office of Public Insurance Counsel recommends keeping copies of everything submitted and sent, dated and organized. State insurance regulators, including the California Department of Managed Health Care and the New York State Department of Financial Services, publish their own appeal checklists that can serve as useful supplementary guides depending on where you live.

Counter the Denial Rationale Directly

Pull the insurer’s specific denial language and respond to each point. If the denial says the service “lacks clinical evidence of effectiveness,” cite the peer-reviewed studies showing it does. If it says “alternative treatments exist,” document why those alternatives are inappropriate for this patient. The InterQual and MCG clinical criteria tools are frequently what insurers use internally; asking your doctor whether the clinical picture meets those criteria can sharpen the rebuttal.

Free assistance programs are worth knowing about. The Patient Advocate Foundation operates a national network of case managers who help patients navigate insurer disputes at no charge. Many states also fund Consumer Assistance Programs (CAPs) specifically authorized under the ACA to help draft appeals, and nonprofits such as the Community Service Society in New York provide similar services. According to the Community Service Society, their advocates sometimes work through thousands of pages of medical records to write 15- to 20-page appeal letters on behalf of patients, a level of detail that generic form letters cannot match.

Submitting Your Appeal and Tracking the Response

Proper submission matters more than most people realize. A technically defective appeal can be rejected on procedural grounds before anyone reads the clinical arguments.

Send the appeal by certified mail with return receipt or through the insurer’s secure online portal if one is available, and keep every confirmation. Include a cover page that clearly states your name, member ID, claim number, date of service, and the specific reason you are appealing. Call the insurer’s member services line after submission to confirm receipt and ask for the name and contact information of the appeals unit handling your case. Note the date, time, and representative’s name from every call.

If the insurer misses its response deadline (typically 30 to 60 days for a standard internal appeal, depending on whether the claim is pre- or post-service), that is itself a regulatory violation you can report to your state insurance department. Insurers operating under state charters, including plans sold through Kaiser Permanente, Molina Healthcare, or Centene subsidiary networks, are subject to state market conduct oversight, and documented deadline violations can support a formal complaint. Our overview of how medical insurance works covers how plan administrators are supposed to communicate during claim disputes.

Escalating to External Independent Review

If the insurer upholds the denial after your internal appeal, the next step is external independent review by an Independent Review Organization (IRO). This is where the odds shift more meaningfully in the consumer’s favor.

How External Review Works and Who Does It

An IRO is a third-party organization accredited by URAC or a similar body, contracted to review denials without any financial relationship with the insurer. Reviewers are typically board-certified physicians in the relevant specialty. Under the ACA, you generally have 4 months from the internal denial notice to request external review. The insurer cannot charge you a fee for this process, and the IRO’s decision is binding on the insurer in most states and for most plan types.

The Pennsylvania Insurance Department reported that its independent external review program helped hundreds of consumers receive benefits that had originally been denied, citing the program as a meaningful consumer protection tool, per a Pennsylvania Insurance Department announcement. The numbers nationally support that. Among Medicare Advantage plans in 2024, 80.7% of appealed prior authorization denials were at least partially overturned, according to KFF’s Medicare Advantage authorization analysis. The Centers for Medicare and Medicaid Services (CMS) administers the Medicare Advantage program and sets the federal standards that govern these review rights.

A quick illustration of why escalation matters: if insurers upheld 66% of internal appeals in 2024, that means about 34 of every 100 internally appealed denials were overturned at that stage. For the remaining 66 that were upheld internally, external review data suggests the majority of those that were escalated were later reversed. Consumers who stop at the internal denial are leaving a meaningful chance of recovery on the table.

One honest limitation worth naming: external review is most powerful for medical necessity disputes. It is less effective when the denial rests on a clear plan exclusion, a service the policy simply does not cover at all. In those cases, the IRO’s authority is narrower, and the more productive path may be a state insurance department complaint arguing that the exclusion itself violates state or federal law, or consulting an attorney about a potential parity claim.

Free Consumer Assistance Programs

Many states offer free Consumer Assistance Programs (CAPs) that can walk you through the external review process or file on your behalf. These programs were established under the ACA and are staffed by trained patient advocates. The Patient Advocate Foundation and the Community Service Society are among the nonprofits providing this kind of help at no cost to patients.

If external review also fails, options still exist. You can file a complaint with your state Department of Insurance, contact your state’s insurance commissioner, or consult an attorney if you believe the insurer acted in bad faith or violated mental health parity laws under the Mental Health Parity and Addiction Equity Act (MHPAEA). The U.S. Department of Labor enforces MHPAEA compliance for employer-sponsored plans, and documented parity violations have supported litigation in several federal circuits. When all formal appeals are exhausted, it is also worth negotiating directly with the provider for a cash-pay discount or exploring hospital charity care programs. As coverage pressures grow, more consumers are facing these situations; our article on how medical coverage is shrinking as costs rise provides broader context on why denials have become so common.

Handling Urgent Medical Needs with Expedited Appeals

Standard appeal timelines assume you can wait weeks for a decision. When the denial involves care that is immediately needed to protect life, health, or bodily function, the rules change.

Qualifying for Expedited Review

To trigger an expedited internal appeal, your treating physician must certify that the standard timeframe would seriously jeopardize your life, health, or ability to regain full function. Insurers are legally required to respond within 72 hours under these circumstances. Expedited external review follows a similarly compressed timeline and can sometimes run concurrently with the internal appeal for pre-service denials. Submit the expedited request in writing and have your physician call the insurer’s medical director line directly, as this direct provider-to-physician contact frequently accelerates review in practice.

If the expedited request itself is denied (meaning the insurer decides the situation is not urgent enough), you have the right to appeal that determination as well. Document every contact, every response, and every stated reason. That record becomes essential if you later need to involve a regulator or attorney, including the Office of Inspector General (OIG) at the Department of Health and Human Services, which investigates patterns of improper denials in federal programs. For anyone selecting a plan where these protections are built in from the start, our comparison of HMO vs. PPO health insurance plans covers how plan type affects your access to specialists and the appeals process.

If your plan type affects how these rights apply to you, it is worth also understanding how health insurance options for self-employed workers differ, since individual marketplace plans carry the strongest ACA-based appeal protections of any coverage category.

Frequently Asked Questions

How long do I have to appeal a denied health insurance claim?

For most ACA-regulated plans, you have 180 days from the date of the denial notice to file an internal appeal. After the internal appeal is decided, you typically have 4 months to request external independent review. Check your denial letter and Summary of Benefits and Coverage for plan-specific deadlines, since ERISA-governed self-funded employer plans may use different timeframes.

What is the difference between an internal appeal and an external review?

An internal appeal goes back to the insurer itself, which reviews the denial using its own staff and clinical criteria. An external review is conducted by an accredited Independent Review Organization with no financial relationship to the insurer. External review decisions are generally binding on the insurer, making it the stronger escalation option when the internal appeal fails.

Can I appeal a denial for a service my doctor says I need?

Yes, and a “not medically necessary” denial is one of the most commonly overturned on appeal. The key is having your physician write a detailed letter that cites specific clinical guidelines, documents what was tried previously, and directly addresses the insurer’s stated criteria. A generic letter of support rarely changes the outcome.

What if my employer’s health plan denies my claim?

If your employer self-funds its health plan, it is governed by ERISA rather than state insurance law, which limits your access to state-mandated external review. You still have federal internal appeal rights under ERISA, and after exhausting those, you can file a complaint with the U.S. Department of Labor or pursue a federal civil action. Fully insured employer plans follow the same ACA appeal rules as marketplace plans.

Are there free resources to help me appeal a denied claim?

Many states operate free Consumer Assistance Programs funded under the ACA that can explain your denial, help you draft an appeal, or even file on your behalf. Nonprofit patient advocacy organizations, like the Community Service Society in New York and the Patient Advocate Foundation, provide similar services at no cost. Your state’s Department of Insurance website is the best starting point for finding local resources.

What happens if every level of appeal is denied?

After exhausting internal and external review, you can file a formal complaint with your state Department of Insurance or, for ERISA plans, the U.S. Department of Labor. If the denial involves a mental health or substance use disorder benefit, a parity violation under the Mental Health Parity and Addiction Equity Act may support a legal claim. It is also worth asking your provider directly about charity care programs or cash-pay discounts as a parallel track while appeals are pending.