Getting a claim denied feels like hitting a wall. But here's what insurers don't advertise: about 40% of denied claims are overturned on appeal. The system is designed to make you give up — most people do. This guide shows you exactly how to fight back and win.
Insurance companies deny claims for many reasons, not all of them legitimate. Common denial reasons include: "not medically necessary" (the most common, and often reversible), "prior authorization not obtained" (sometimes waivable in emergencies), "out-of-network provider" (capped under the No Surprises Act for emergencies), "experimental or investigational" (often incorrect — check FDA approval), and simple administrative errors like wrong codes or missing information.
The first step is understanding which category your denial falls into, because each requires a different response.
Your insurer is legally required to send you a written denial notice that explains: the specific reason for denial, the clinical criteria or plan language they relied on, and your right to appeal with a deadline.
If you haven't received this, call and request it in writing immediately. You cannot build an effective appeal without knowing exactly what they objected to.
"Not medically necessary" denials are the most winnable. Your doctor's supporting documentation — clinical notes, test results, treatment history, peer-reviewed literature — is your ammunition. Get a letter of medical necessity from your doctor specifically addressing the insurer's stated criteria.
"Prior authorization not obtained" can sometimes be waived retroactively if the situation was urgent or if your provider acted in good faith. The No Surprises Act also restricts surprise PA requirements for emergency care.
"Experimental" denials are worth fighting if the treatment has FDA approval or strong peer-reviewed support. Ask your doctor for literature citations and check whether your state has any clinical trial coverage mandates.
Request your insurer's coverage determination criteria for your specific treatment code. Under ERISA and ACA rules, they're required to give you the clinical criteria they used to make the decision.
Every insurer must offer at least one level of internal appeal. You typically have 180 days from the denial notice to file. Submit your appeal in writing with:
Send everything certified mail. Keep copies of everything. If you can get your doctor to call the insurer's medical director directly (peer-to-peer review), that often speeds up reversals.
BillVeil's AI writes a customized appeal based on your denial reason.
Write Your Appeal Letter (AI) →If your internal appeal is denied, you have the right to an independent external review by a third-party organization that has no financial relationship with your insurer. Under the ACA, this right applies to most private health plans.
External review organizations overturn insurer decisions about 40% of the time for clinical denials. File within 60 days of your final internal denial. Your insurer must tell you how in the denial letter.
For Medicare appeals, the process is slightly different — you can escalate through the Medicare Appeals Council all the way to federal court if needed.
File a complaint with your state insurance commissioner — insurers take these seriously because commissioners have enforcement power. Your state may also have a patient advocate or insurance ombudsman who can intervene on your behalf for free.
If you have an employer-sponsored plan governed by ERISA, you can ultimately sue in federal court if all appeals are exhausted — though most cases are resolved before that point.
BillVeil has 44 free AI tools to analyze your bill, write letters, and fight back.
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