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Insurance Claim Denied? Here’s Exactly What to Do

By AppealGen Editorial Team  ·  June 1, 2026  ·  11 min read

Your health insurance claim was denied. Before you panic, accept it, or pay out of pocket — read this. Insurance companies deny approximately 850 million claims per year, yet fewer than 1% of patients ever file a formal appeal. That gap is entirely avoidable. This guide tells you exactly what to do, in order, starting today.

Table of Contents
  1. Step 1: Read the Denial Letter Carefully
  2. Step 2: Identify Your Denial Type
  3. Step 3: Note Your Appeal Deadline
  4. Step 4: Gather Your Documentation
  5. Step 5: Write and Submit Your Appeal
  6. Step 6: If Your Internal Appeal Fails
  7. Frequently Asked Questions
59%
of internal insurance appeals are won by the patient — yet most people never file one. Insurers count on your silence.
KFF Analysis of ACA Marketplace Denials, 2023

Step 1: Read the Denial Letter Carefully

Your insurer is required by law to send you a written denial notice (Explanation of Benefits or denial letter) that contains specific language determining your entire appeal strategy. Do not skip it.

What to look for:

📝 Important

Save every piece of correspondence from your insurer — every denial letter, EOB, and phone call note (date, time, representative name). This trail matters if you escalate to external review or a state insurance commissioner complaint.

Step 2: Identify Your Denial Type

The denial reason dictates your appeal strategy. A medical necessity denial requires a different letter than a prior authorization denial.

1
Not Medically Necessary
Often applied algorithmically without physician review. Your rebuttal must present objective clinical evidence, documented failed alternatives, and references to established clinical guidelines. Full guide →
2
No Prior Authorization
Your appeal should argue retroactive authorization based on medical necessity and demonstrate the treatment met all clinical criteria. Full guide →
3
Experimental or Investigational
Establish FDA approval status, cite professional society guidelines endorsing the treatment, and show it is widely accepted standard-of-care for your diagnosis.
4
Out-of-Network
Arguments include lack of qualified in-network alternatives, emergency circumstances, continuity of care requirements, and ACA protections for out-of-network emergency services.
5
Insufficient Documentation
Often the easiest denial to overturn — submit the complete clinical record with a cover letter organizing the documentation clearly and resubmit as a formal appeal.

Step 3: Note Your Appeal Deadline

Under the ACA, most health plans must allow at least 180 days from the denial notice to file an internal appeal. But your plan may have different rules.

⏳ Deadline Warning

Do not assume you have 180 days. Check your specific denial letter for your exact filing deadline. Missing it means you lose your appeal rights entirely. See our Insurance Appeal Deadlines by State guide for full state-by-state rules.

Step 4: Gather Your Documentation

💡 Tip

Ask your doctor’s office to arrange a peer-to-peer review — a direct clinical discussion between your physician and the insurer’s reviewer. Studies show dramatically higher overturn rates when peer-to-peer review occurs.

Step 5: Write and Submit Your Appeal Letter

Your appeal letter must directly address the stated denial reason, present evidence that rebuts it, and be formatted professionally. Generic “I disagree” letters are almost universally rejected.

Every effective appeal letter must include: your identifying information; the specific denial reason you’re appealing (quoted exactly); your direct clinical rebuttal; a clinical guideline citation; and a request for peer-to-peer review. See our full letter-writing guide and sample letters for complete examples.

Generate Your Appeal Letter in 10 Minutes

AppealGen structures your appeal around the exact denial reason in your letter. Upload your denial letter, answer a few clinical questions, and we build the full professionally written letter. Free to start.

Start My Appeal →

Step 6: If Your Internal Appeal Also Fails

Under the ACA and most state insurance laws, you have the right to an external review by an independent organization. Their determination is legally binding on the insurance company.

See our full Know Your Rights guide and Appeals Guide for the complete external review process.

Frequently Asked Questions

What should I do first when my insurance claim is denied?
Read your Explanation of Benefits (EOB) or denial letter carefully to identify the exact denial reason. The specific language determines your entire appeal strategy. Don’t appeal until you understand precisely why the claim was denied.
How long do I have to appeal a denied insurance claim?
Under the ACA, most health plans must allow at least 180 days from the denial notice. Check your specific denial letter — your plan may have shorter or longer deadlines. For urgent situations you may qualify for an expedited decision within 72 hours.
What is the success rate for insurance denial appeals?
KFF data shows insurers overturn their own decisions in approximately 59% of internal appeal cases. Medical necessity denials with full clinical documentation have overturn rates of 70–83%.
What if my internal appeal is also denied?
You have the right to request external review by an independent organization not affiliated with your insurer. External reviewers overturn insurer decisions in 40–60% of cases and their decision is legally binding.
About this guide: Prepared by the AppealGen editorial team based on KFF, AMA, and Commonwealth Fund insurance denial research, ACA and ERISA federal requirements, and review of 1,000+ real denial cases across major US insurers. Updated June 2026.