Federal guide · health insurance denial
If your health insurer denied a claim, refused prior authorization for care you need, or sent you a rejection letter full of acronyms — you have appeal rights that work. Most denials are not reviewed by a doctor before they're issued. Most denials are reversed when patients appeal. The system depends on patients not knowing this.
Typical recovery
Coverage of the denied service / refund of out-of-pocket payments
Typical timeline
DIY: 30–180 days through internal + external review
You are not alone
Health-insurance denials are one of the largest engineered injustices in American life. Roughly one in six in-network claims gets denied. Studies tracking patient response have repeatedly found that fewer than 1% of denials are ever appealed — and yet, of the small fraction of denials that are appealed, a significant majority are reversed in the patient's favor. The arithmetic is grotesque: insurers are denying tens of millions of claims a year that they would lose on appeal, and they know it, because almost nobody appeals.
The reason almost nobody appeals is that the system is designed to make appealing as exhausting as possible. Denial letters arrive in a kind of bureaucratic fog: they tell you the claim was denied, they cite a code, and they reference plan language that you've never read. They don't tell you, clearly, what the actual reason was. They don't tell you the deadline to appeal — which is often shorter than people assume, sometimes 60 or 90 days, sometimes 180. They don't tell you that you have a right to internal appeal, and after that an external review by an independent reviewer, and that the external reviewer is often a doctor in the relevant specialty who has no financial stake in the outcome. They don't tell you that the medical records you can request — and that you should request — often show that nobody at the insurance company actually looked at your case before the denial was issued.
The reason this works as a business model is the same as in every other consumer-protection space: most people are tired. You are tired because you are sick, or because someone you love is sick, or because the care you need has now been delayed by weeks while you fight a paperwork battle you didn't sign up for. The denial often comes after you've already received the care, in which case the insurer is essentially asking you to pay tens of thousands of dollars out of pocket for something you reasonably believed was covered. Sometimes the denial comes before — refusing prior authorization for a treatment your doctor has recommended — and the timing weaponizes the medical urgency against you. The longer you wait, the worse you get; the more time you spend appealing, the less time you spend healing.
The reversal rate on external review — when an independent doctor actually looks at the case — is the closest thing in this entire system to a "tell." When the people making the decisions have no financial incentive to deny, denials drop dramatically. That gap is the unfairness, and it is documented. Knowing the gap exists is, in many ways, the entire battle. Once you know that the denial in your hand was issued by a clerk reading a flowchart and that an external reviewer is statistically likely to overturn it, the path forward stops feeling impossible.
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The playbook
01
Two documents matter most: your Explanation of Benefits (EOB) for the denied claim, and the denial letter the insurer is required to send. The denial letter must include the specific reason for denial, the plan provisions it relied on, and your appeal rights and deadlines. If the letter is missing any of this, that's itself a violation worth raising. Get both documents in your possession before you do anything else.
02
Denial reasons fall into a small number of categories: 'not medically necessary,' 'experimental/investigational,' 'not a covered benefit,' 'prior authorization required,' 'out-of-network,' 'coding error,' 'duplicate claim,' 'timely-filing error.' Each has a different appeal strategy. Many denials are administrative (coding errors, timely-filing errors) and can be resolved by your provider's billing office without a full appeal. Identifying the real reason — not the boilerplate — determines which path you take.
03
Send a written request to the insurer asking for the complete claim file: the medical records they reviewed, the internal medical reviewer's notes, the clinical guidelines they applied, and the credentials of the reviewer who issued the denial. Federal and state law require they provide this for ERISA plans and most state-regulated plans. You will frequently find that the 'medical reviewer' had no specialty in the relevant field, or that the guidelines they applied are outdated, or that no human reviewer actually looked at the file at all.
04
The single most powerful piece of evidence in most appeals is a detailed letter from the prescribing physician explaining why the denied service was medically necessary, what the alternatives are (and why they were rejected), and what evidence in the medical literature supports the recommended treatment. Most providers will write this if you ask — they want their patients to receive care they've recommended. The letter should reference specific peer-reviewed studies and clinical guidelines.
05
The internal appeal letter should: identify the claim and denial, state the specific basis on which you're appealing, attach the medical records and the letter of medical necessity, and address each ground the insurer cited for the denial. Be explicit and organized. Send certified mail with return receipt in addition to any required electronic submission. The insurer's response window is typically 30 days for retrospective claims and faster (often 72 hours) for urgent prospective denials.
06
If the internal appeal is denied, you have a right to external review by an independent reviewer who is not affiliated with the insurer — typically a board-certified physician in the relevant specialty. External review is statistically the most likely place to win, because the reviewer has no financial stake in the outcome. The deadline to request external review is typically 60–180 days from the internal-appeal denial. Don't miss it.
07
Whether or not your appeal is succeeding, file a complaint with your state's Department of Insurance (or, for self-funded employer plans, with the federal Department of Labor). State insurance departments have leverage with insurers that consumers do not — and a regulator complaint often produces faster movement than the formal appeal process alone. It also creates a public record that aggregates against the insurer over time.
08
If your denial is for prior authorization on a treatment that hasn't happened yet, your provider can usually request a 'peer-to-peer' review with the insurer's medical director. The peer-to-peer is a phone call between your doctor and the insurer's reviewer, and it resolves a substantial share of prior-authorization denials within days — much faster than written appeal. Push your provider to request one for time-sensitive denials.
The honest part
Insurance appeals are the most paperwork-intensive consumer process most people will ever attempt.
The structure of appeals is layered: there is an internal appeal (sometimes two — first-level and second-level), then an external review by an independent reviewer, and in some plans an additional grievance process. Each layer has its own deadline (typically 60–180 days from the prior decision), its own form requirements, its own evidentiary standards. The deadlines are tight enough that missing one can cost you the entire appeal. The evidentiary requirements are heavy enough that an ordinary appeal letter won't carry the day — you need to attach the relevant medical records, the prescribing doctor's notes, peer-reviewed evidence supporting the medical necessity of the care, and (often) a detailed argument about why the insurer's stated reason for denial is inconsistent with their own plan language.
The information asymmetry is brutal. Your insurer has every record of your care, every code that was billed, every internal review note, every guideline they relied on. You have a denial letter, an EOB, and whatever your provider gave you. To appeal effectively, you need to request your full claim file from the insurer — including the internal medical reviewer's notes, the guidelines they applied, and the credentials of the person who made the decision. Most patients don't know this is requestable. Insurers don't volunteer it.
A clean DIY appeal cycle takes 15–30 hours of focused work over 2–6 months, much of it spent on coordination: getting records from your provider, getting documents from the insurer, drafting the appeal, getting your provider to write a letter of medical necessity, tracking the deadlines for the next level if you lose. It is the kind of work that can absolutely be done — and can absolutely save tens of thousands of dollars — but it asks you to operate as a part-time medical lawyer during one of the worst stretches of your adult life.
Common questions
An internal appeal is reviewed by the insurance company's own staff — it's the first formal layer of appeal and is the one your denial letter will reference. An external review is conducted by an independent reviewer (usually a board-certified physician in the relevant specialty) who is not affiliated with the insurer. External reviews exist because internal reviews tend to confirm internal decisions, and the system needs an independent backstop. External reviews reverse a substantial share of upheld denials.
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Last updated 2026-05-05