Nearly 1 in 5 health insurance claims get denied. Most people never appeal. Here's a step-by-step breakdown of what to do when your insurer says no.
The Odds Are in Your Favor (If You Fight Back)
Getting a denial letter from your health insurance company feels like a door slamming shut. You followed the rules, saw the right doctor, got the referral, and still: denied.
You're not alone. According to KFF, ACA marketplace insurers denied approximately 19% of in-network claims in 2024, roughly 8.8 million rejected claims out of 46 million submitted. And that's just the marketplace. Private payer denial rates have been climbing steadily, rising from 8% to 11% between 2021 and 2023.
Here's the part most people don't know: the system is designed for you to give up. Most people never appeal a denied claim. But when they do, the numbers flip. The American Medical Association's 2024 Prior Authorization Physician Survey found that over 80% of prior authorization appeals ultimately succeed when pursued.
Over 80%. The insurance company is betting you won't push back.
Step 1: Read the Denial Letter Carefully
Every denial letter is required to include the specific reason your claim was denied. Common reasons include: the treatment was deemed "not medically necessary," it was classified as experimental, the wrong billing code was used, or prior authorization wasn't obtained.
The reason matters because your appeal needs to address it directly. Don't write a general complaint. Respond to the exact criteria they cited.
Step 2: Understand Your Appeal Deadlines
For most plans, you have 180 days from the date of the denial to file an internal appeal. Don't sit on it. The clock starts when the denial is issued, not when you read it.
You should receive confirmation that your appeal was received within 7-10 days. If you don't, call your insurer and confirm it's in their system. Document the date, time, and name of the representative you spoke with.
Step 3: Gather Your Evidence
This is where most appeals succeed or fail. You need more than a letter saying "I disagree." Strong appeals include your doctor's letter of medical necessity, relevant medical records, published clinical guidelines or peer-reviewed research supporting the treatment, and a direct response to the insurer's stated denial criteria.
Number and label every attachment. Reference them by number in your letter. Make it easy for the reviewer to follow your case.
Step 4: Write a Clear, Factual Appeal Letter
Include your full name, policy number, claim number, date of service, and the denial reference number. Open with a clear statement: you are appealing the denial of a specific treatment issued on a specific date.
Address the denial reason head-on. If they said the treatment wasn't medically necessary, present the evidence that proves otherwise. Keep the tone professional. Short, factual statements work better than emotional language.
End with a clear ask: full coverage of the denied claim, reprocessing with corrected codes, or authorization for the pending treatment.
Step 5: Know Your Escalation Options
If your internal appeal is denied, you have the right to an external review by an independent third party. This is separate from the insurance company, and their decision is binding.
Some states also have a Department of Insurance that accepts complaints and can intervene. Check your state's insurance commissioner website for complaint filing procedures.
The Bottom Line
A denial is not a final answer. It's the beginning of a process. The system counts on you being overwhelmed and walking away. But the data shows that persistence works, and the appeal process is your legal right.
If writing the appeal letter feels intimidating, you don't have to start from scratch. The Health Insurance Appeal Kit includes 8 editable letter templates covering the most common denial scenarios, from medical necessity disputes to prior authorization issues. Each template walks you through what to include, how to structure your argument, and what language to use. $14.99.
This post is for informational purposes only and does not constitute legal or medical advice. Insurance regulations vary by state and plan type. Consult a licensed professional for advice specific to your situation. Information current as of April 2026.