Receiving a health insurance denial feels like a gut punch — especially when you're already dealing with a medical situation. But a denial is not final. Understanding exactly why your claim was denied is the first step to reversing it.
What the Denial Letter Must Tell You
Under federal law (the ACA and ERISA), your insurer is required to tell you:
- Exactly why the claim was denied (the specific reason code and plain-language explanation)
- Which plan provision the denial is based on (the specific exclusion, limitation, or coverage requirement)
- How to appeal — deadlines, process, and contact information
- Your right to external review if internal appeals fail
If your letter doesn't include all of this, call your insurer and ask for a complete written explanation.
Common Denial Reasons and What They Mean
"Not Medically Necessary"
The insurer's medical reviewers decided the service didn't meet their criteria for medical necessity — even if your doctor says it is. This is the most commonly appealed and reversed denial reason.
How to fight it: Ask your doctor to write a Letter of Medical Necessity explaining why the treatment is required for your specific condition. Include clinical guidelines, peer-reviewed studies, and your diagnosis history.
"Service Not Covered / Exclusion"
The service is specifically excluded from your plan (cosmetic procedures, experimental treatments, some dental/vision services).
How to fight it: Review your Summary of Benefits and Coverage carefully. Sometimes what looks like an exclusion has exceptions. If the service is medically necessary and your doctor ordered it, an appeal is still worth filing.
"Prior Authorization Required"
The service needed advance approval from your insurer and didn't get it — often a procedural denial rather than a coverage denial.
How to fight it: Ask your doctor's office to submit a retroactive prior authorization request. Insurers often grant these if the service was clinically appropriate.
"Out-of-Network Provider"
You saw a provider not in your plan's network and are being held to out-of-network cost-sharing.
How to fight it: If you didn't have a reasonable in-network option (emergency, specialist shortage, no in-network provider available), request an exception. The No Surprises Act (2022) also protects patients from unexpected out-of-network bills in many situations.
"Coordination of Benefits"
If you have multiple insurance plans, one insurer is claiming the other should pay first.
How to fight it: Get both insurers on the phone and clarify which is primary. Once coordination is established, the claim should process.
"Duplicate Claim"
The insurer thinks this claim was already submitted and paid. This is often a billing error on the provider's end.
How to fight it: Call your provider's billing department and your insurer. Ask both to trace the original claim and confirm payment status.
"Timely Filing"
The claim was submitted after the plan's filing deadline.
How to fight it: Provide documentation showing when the service occurred and when the claim was submitted. If the delay was due to provider error, ask the provider to submit a corrected claim with an explanation.
The Appeals Process
Step 1: Internal Appeal
File an appeal with your insurer within their stated deadline (usually 180 days for most claims). Your appeal should include:
- A clear statement that you're appealing and why
- A letter from your doctor supporting the medical necessity
- Any clinical guidelines or peer-reviewed research supporting the treatment
- Copies of any prior authorizations you received
- Your EOB and the original denial letter
Step 2: Expedited Appeal (for Urgent Situations)
If you need the service urgently (ongoing treatment, imminent hospitalization), you can request an expedited appeal. Insurers must respond within 72 hours.
Step 3: External Review
If your internal appeal is denied, you have the right to an independent external review by a third-party organization. The insurer must abide by the external reviewer's decision. Request external review within 60 days of the final internal denial.
Step 4: State Insurance Commissioner Complaint
If you believe the denial was wrongful, file a complaint with your state's department of insurance. This creates a formal record and often prompts the insurer to reconsider.
Appeal Success Rates
According to the Kaiser Family Foundation, approximately:
- Less than 1% of eligible denials are appealed
- Of those appealed, about 40% are reversed in the consumer's favor
The lesson: appeal. Most people don't, and insurers count on that.
Tips That Improve Appeal Success
- Be specific — reference the exact denial reason code and the plan provision
- Get your doctor involved — clinical letters from providers carry significant weight
- Meet deadlines — missing an appeal deadline forfeits your right to challenge
- Document everything — keep records of all communications, names of representatives, and dates
- Request your claim file — you're entitled to a complete copy of all documents related to your claim
Got a denial letter that's hard to parse? PaperLens reads any insurance document and explains exactly why your claim was denied and what your options are. Scan your denial letter →