What to Do If Your Insurance Denied the Claim

A denial is a decision, not a verdict

When an insurance claim is denied, the provider can bill the patient for the full amount. But a denial is one payer's decision on one submission — it can be appealed, often successfully. Most denials are reversed or corrected when patients push back with the right documentation.

The key mindset shift: an insurance denial is an automated or lightly reviewed decision, not a considered medical judgment. Claims are processed against contract rules and coding logic, and legitimate claims get denied every day because a code was wrong, a checkbox was missed, or the reviewer followed policy instead of the patient's record. The appeal is where the human decision happens.

Read the denial code

The denial notice lists a reason code: not medically necessary, out-of-network, missing authorization, wrong coding, or coverage limit reached. Each reason has a different fix. Match your appeal to the reason — a medical-necessity denial needs clinical documentation; a coding denial needs the claim corrected and resubmitted.

• Not medically necessary — appeal with clinical records and a provider letter.
• Out-of-network — check No Surprises Act protections or in-network verification.
• Missing prior authorization — request retro-authorization.
• Wrong or missing codes — have the provider correct and resubmit.
• Coverage limit reached — appeal based on medical necessity.

File the internal appeal before the deadline

Most employer group plans allow 180 days from the date of the claim decision to file an internal appeal. Medicare Advantage allows 60 days. The window is on your denial letter — mark it and don't miss it. File in writing with all supporting documents and keep the reference number.

File online through your insurer's appeals portal if it exists — it gives you an instant reference number and confirmation receipt — and keep a copy of everything you submit. If you file by mail, use certified mail. Either way, your goal is proof that the appeal was filed within the window, because the deadline is the one thing an insurer won't bend on.

Build the appeal file

A strong appeal includes your denial letter, the provider's clinical records, a letter from your doctor explaining medical necessity in plain language, and any test results or notes that support the service. Insurers decide appeals on documentation — the more complete and specific, the better.

The doctor's letter is the single most persuasive document, and it should be written for a reviewer who wasn't at the visit: it needs to say why the service was needed, what the alternatives were and why they wouldn't have worked, and what the risk was of not providing it. Offer to have your provider supply it — most practices will, because a successful appeal means they get paid.

1. 1Read the denial code and confirm the appeal deadline.
2. 2Request your full medical records from the provider.
3. 3Ask your doctor for a letter of medical necessity.
4. 4File the written internal appeal with all documentation.
5. 5If denied again, request external review.

External review is your safety net

If the internal appeal fails, federal law gives most patients the right to an external review by an independent organization that isn't connected to your insurer. Request it in writing within the stated window. External reviews overturn some denials, and the process is free to you.

Coordinate with the provider

Tell the billing office about the appeal in writing and ask them to hold collection while it's pending. Providers often resubmit corrected claims and can be your ally — a provider that wants to be paid will help you appeal a denial.

Expedited appeals for urgent care

If the denial affects ongoing or urgent treatment, you can request an expedited appeal, decided within 72 hours. Ask your provider to flag the urgency in writing.