How to Fight a Health Insurance Denial — and Win
Getting a denial letter doesn't mean it's over. Over 50% of insurance denials that are appealed are overturned. Here's the exact process — from someone who processed claims from the inside — to fight back and get the coverage you're owed.
Most insurance plans give you between 30 and 180 days from the denial date to file an internal appeal. Missing that window can permanently forfeit your right to challenge the decision. Use the deadline calculator on this page to find yours before you do anything else.
The 6 Most Common Types of Insurance Denials
Before you appeal, you need to understand why your claim was denied. Your denial letter must state the reason by law. Find your denial type below — each one requires a slightly different appeal strategy.
Medical Necessity Denial
The insurer says the treatment wasn't medically necessary. This is the most common — and most winnable — denial. Your doctor's documentation is your strongest weapon.
Prior Authorization Denial
The service required pre-approval that wasn't obtained. Can be appealed if your doctor can show it was urgent, or if the authorization process was unclear.
Out-of-Network Denial
You saw a provider outside your network. Appealable if it was an emergency, if no in-network provider was reasonably available, or if you were misled about network status.
Experimental / Investigational Denial
The insurer says the treatment is experimental. Fight this with peer-reviewed medical literature and a letter from your doctor stating it is the established standard of care.
Coverage Exclusion Denial
The insurer claims the service isn't covered under your plan. Request the exact policy language in writing and compare it carefully to what your doctor documented.
Coding / Administrative Error
A billing code was entered incorrectly. These are often resolved with a single phone call — ask the billing department to resubmit with the corrected code before filing a formal appeal.
How to Appeal an Insurance Denial in 6 Steps
Follow these steps in order. The first two steps — getting the denial in writing and understanding the specific reason — determine the entire strategy for your appeal.
Get the denial in writing and read it carefully
If you received a verbal denial by phone, request a written Explanation of Benefits (EOB) and a formal denial letter immediately. By law, the denial letter must state the specific reason for the denial, the clinical criteria or plan provision used to make the decision, and information about how to appeal. If the letter is vague or doesn't include all of this, call your insurer and demand a more detailed explanation in writing.
Request the clinical criteria used to deny your claim
Your insurer used specific clinical guidelines to decide your treatment wasn't medically necessary or covered. You have the right to request these criteria in writing. Ask for the exact guidelines, criteria, or policy provisions they relied on to make the denial decision. Once you have them, compare them against your doctor's notes and treatment records — this is where you will find the gaps in their reasoning.
Get a Letter of Medical Necessity from your doctor
This is the single most powerful document in any insurance appeal. Ask your doctor to write a detailed letter explaining why the treatment was medically necessary specifically for your condition, what alternatives were considered and why they were inadequate, what the consequences of not receiving the treatment would be, and any relevant clinical guidelines or published research that supports their recommendation. The more specific this letter is to your situation — not a generic template — the stronger your appeal.
File your internal appeal in writing — before the deadline
Every insurance plan must have an internal appeals process. File your appeal in writing — not just by phone — and send it by certified mail so you have proof of the date. Your appeal letter should state the denial you are appealing and the claim number, clearly explain why the denial was incorrect, reference your doctor's Letter of Medical Necessity, include any supporting medical records, and request a response within the legally required timeframe (usually 30–60 days for non-urgent appeals, 72 hours for urgent care).
If the internal appeal fails — request an external review
If your insurer upholds the denial after your internal appeal, you have the right to an Independent External Review under the Affordable Care Act. This means an independent organization — not your insurer — reviews your case and makes a binding decision. Your insurer must comply with the external reviewer's ruling. Request the external review within 60 days of the final internal denial. There is no cost to you for this process.
Escalate further if needed
If external review doesn't resolve it, you have additional escalation paths. File a complaint with your state's Insurance Commissioner — they regulate insurer conduct and can apply pressure. Contact your state's Consumer Assistance Program (CAP) for free help with appeals. If the denial involves a large amount, consult a patient advocate or healthcare attorney — many work on contingency for insurance disputes. For employer-sponsored plans, contact your HR department — employers have leverage with insurance companies that individual members do not.
✓ Appeal progress checklist — tap each item as you complete it
⏰ Appeal Deadline Calculator
Enter your denial date and plan type to see your key deadlines. Missing these dates can permanently forfeit your right to appeal.
Generate Your Insurance Appeal Letter
Fill in your details below and get a complete, professional appeal letter ready to send to your insurance company. Written in the language insurers respond to — from someone who has seen what works from the inside.
📞 Phone Script — What to Say When You Call Your Insurer
Use this before you file your written appeal. A phone call often surfaces information that strengthens your case — and occasionally resolves the denial outright.
Free Insurance Denial Action Kit
Get the complete denial appeal toolkit — including a denial reason decoder, a deadline tracker template, and a checklist of supporting documents to include in every appeal.
- Denial reason decoder (plain English)
- Appeal deadline tracker template
- Supporting documents checklist
- External review request guide
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