Your Insurance Denied Your Claim — Here Is How to Fight Back and Win
Receiving a claim denial from your insurance company feels like a door slamming shut. You needed medical care, you received it, and now your insurance company is telling you they will not pay for it. The bill lands squarely on you.
But here is what the insurance company does not want you to know: more than half of all insurance appeals are successful. According to data from the Kaiser Family Foundation and various state insurance departments, patients who appeal denied claims win approximately 50-60% of the time for internal appeals and 40-55% of the time for external appeals. Yet fewer than 1% of patients ever file an appeal.
That gap — between the high success rate of appeals and the tiny percentage of patients who actually appeal — represents billions of dollars in claims that should have been paid but were not, simply because patients did not know they could fight back.
Why Claims Get Denied
Understanding why your claim was denied is the first step in crafting a successful appeal. Here are the most common denial reasons and what they actually mean:
Medical Necessity
What the denial says: "The requested service is not medically necessary."
What it actually means: The insurance company's medical reviewer (often a nurse or physician who has never examined you) has determined that the service was not required based on your diagnosis. This is the most common denial reason and also the most commonly overturned on appeal.
How to fight it: Get a letter from your treating physician explaining why the service was medically necessary for your specific condition. Include relevant medical literature, clinical guidelines, and your medical records.
Prior Authorization
What the denial says: "Prior authorization was not obtained."
What it actually means: The provider was supposed to get pre-approval from the insurance company before performing the service but did not. This is generally the provider's responsibility, not yours.
How to fight it: Contact the provider and ask them to submit a retroactive prior authorization request. If they refuse, file an appeal arguing that the service was medically necessary and that you should not be penalized for the provider's administrative failure.
Out-of-Network
What the denial says: "The provider is not in your plan's network."
What it actually means: The provider does not have a contract with your insurance company. However, if you were treated by an out-of-network provider in an emergency or at an in-network facility, the No Surprises Act may protect you.
Experimental or Investigational
What the denial says: "The requested service is considered experimental or investigational."
What it actually means: The insurance company does not consider the treatment to be standard of care. This denial is common for newer treatments, off-label drug uses, and certain surgical techniques.
How to fight it: Provide evidence that the treatment is accepted in the medical community — peer-reviewed studies, clinical guidelines from professional medical societies, and letters from specialists.
Not Covered Under Your Plan
What the denial says: "This service is not a covered benefit under your plan."
What it actually means: Your specific insurance plan does not include coverage for this type of service. This is harder to appeal because it is a plan design issue rather than a medical judgment. However, you may be able to argue that the service falls under a covered category or that an exception should be made.
| Denial Reason | Appeal Success Rate | Key Evidence Needed |
|---|---|---|
| Medical necessity | 55-65% | Physician letter, clinical guidelines, medical records |
| Prior authorization | 50-60% | Retroactive authorization request, medical necessity documentation |
| Out-of-network | 45-55% | No Surprises Act protections, emergency circumstances |
| Experimental/investigational | 40-50% | Peer-reviewed studies, professional society guidelines |
| Not covered | 30-40% | Plan language interpretation, exception request |
The Two Levels of Appeal
Level 1: Internal Appeal
Your first appeal is reviewed by the insurance company itself — but by a different reviewer than the one who made the original denial. You have the right to:
Submit a written appeal explaining why the denial should be overturned
Include supporting documentation (medical records, physician letters, clinical guidelines)
Request that the appeal be reviewed by a physician in the same specialty as your treating doctor
Timeline: You generally have 180 days from the date of the denial to file an internal appeal. The insurance company must respond within 30 days for pre-service claims (before the service is provided) or 60 days for post-service claims (after the service is provided).
Expedited appeal: If the standard timeline would jeopardize your health (e.g., you need urgent treatment), you can request an expedited appeal. The insurance company must respond within 72 hours.
Level 2: External Appeal (Independent Review)
If the internal appeal is denied, you have the right to an external appeal — an independent review by a third-party organization that has no connection to your insurance company. This is one of the most powerful patient protections in the ACA.
How it works: An independent review organization (IRO) reviews your case, including all medical records and documentation. The IRO's decision is binding on the insurance company — if they rule in your favor, the insurance company must pay the claim.
Timeline: You generally have 4 months after the internal appeal denial to request an external review. The IRO must make a decision within 45 days (or 72 hours for expedited reviews).
Cost: External reviews are free to the patient. The insurance company pays the cost of the review.
How to Write a Winning Appeal Letter
The appeal letter is the most important document in the process. Here is a structure that I have used successfully hundreds of times:
Paragraph 1: Identification
State your name, policy number, claim number, date of service, and the specific denial you are appealing.
Paragraph 2: Summary of the Denial
Briefly describe what was denied and the reason given by the insurance company.
Paragraph 3: Why the Denial Is Wrong
This is the core of your appeal. Address the specific denial reason with evidence:
For medical necessity: Explain why the service was necessary for your condition, citing your physician's recommendation and clinical guidelines
For prior authorization: Explain that the provider's failure to obtain authorization should not result in denial of a medically necessary service
For experimental/investigational: Cite peer-reviewed studies and professional society guidelines supporting the treatment
Paragraph 4: Supporting Evidence
List the documents you are including with the appeal (physician letter, medical records, clinical guidelines, studies).
Paragraph 5: Request
Clearly state what you are requesting — that the denial be overturned and the claim be paid.
Getting Your Doctor to Help
Your treating physician's support is critical to a successful appeal. Here is how to get it:
Ask directly. Call your doctor's office and explain that your insurance denied the claim. Ask the doctor to write a letter supporting the medical necessity of the service. Most doctors are willing to do this — they want their patients to receive the care they recommended.
Provide a template. Make it easy for the doctor by providing a template or outline of what the letter should include:
Your diagnosis and medical history
Why the specific service was medically necessary for your condition
What alternatives were considered and why they were not appropriate
The expected outcome of the treatment
References to clinical guidelines or medical literature
Request a peer-to-peer review. Many insurance companies offer a peer-to-peer review where your doctor can speak directly with the insurance company's medical reviewer. This is often more effective than a written letter because your doctor can answer questions and address concerns in real time. Ask your doctor's office to request a peer-to-peer review.
State Insurance Department Assistance
If your appeal is denied at both the internal and external levels, you still have options:
File a complaint with your state Department of Insurance. The DOI regulates insurance companies in your state and can investigate whether the denial was proper. In some cases, the DOI can compel the insurance company to reconsider.
Request a state-level review. Some states have additional appeal processes beyond the federal requirements. Your state DOI can tell you what options are available.
Contact your state's Consumer Assistance Program (CAP). Many states have CAPs that help consumers navigate insurance disputes. These programs are free and can provide guidance, advocacy, and sometimes direct intervention.
Special Situations
Emergency Services
Under the ACA and the No Surprises Act, insurance companies cannot deny claims for emergency services based on prior authorization or out-of-network status. If your emergency claim was denied, cite these laws in your appeal.
Mental Health and Substance Abuse
Under the Mental Health Parity and Addiction Equity Act, insurance companies must cover mental health and substance abuse services at the same level as medical/surgical services. If your mental health claim was denied with criteria that would not be applied to a medical claim, you may have a parity violation.
Prescription Drugs
If your insurance denied coverage for a prescription drug, you can appeal and also request an exception to the formulary. Your doctor can argue that the specific drug is medically necessary because alternatives have been tried and failed, or because the alternatives are not appropriate for your condition.
Key Takeaways
More than 50% of insurance appeals are successful — but fewer than 1% of patients ever appeal
You have the right to two levels of appeal — internal (by the insurance company) and external (by an independent reviewer)
External appeal decisions are binding — on the insurance company — if you win, they must pay
Your doctor's support is critical — ask for a letter of medical necessity and a peer-to-peer review
You have 180 days — to file an internal appeal and 4 months to file an external appeal
Appeals are free — the insurance company pays for the external review
File a complaint with your state DOI — if both appeal levels are denied
Special protections exist — for emergency services, mental health, and prescription drugs
Never accept a denial as final — the appeal process exists because denials are often wrong