Appealing a denied health insurance claim: a step-by-step guide

The appeals process feels designed to exhaust you. It mostly is. The good news: of patients who actually file, roughly half win at the internal-appeal stage. The losing move is not filing at all.

Read the denial carefully

The Explanation of Benefits will name a reason code. The common ones: 'not medically necessary,' 'experimental,' 'out of network,' or 'missing prior authorization.' The reason determines your strategy.

Gather the right documentation

• Your full plan document (the Summary of Benefits and Coverage is not enough — get the actual policy).
• All medical records related to the service, including notes that show why it was needed.
• A letter of medical necessity from your doctor, written specifically for this appeal — not a generic one.
• Peer-reviewed studies, treatment guidelines, or specialty society recommendations that support the service.

Write the appeal letter

Be brief and specific. State the patient name, member ID, claim number, date of service, and the denial reason. Then refute it point by point with the evidence you gathered. Attach everything. Send by certified mail to the address in your plan document (not the one on the EOB — they're sometimes different).

Watch the clock

Internal-appeal deadlines are short — often 180 days from the denial date, sometimes 60. Diary the deadline and file before it. After internal appeals are exhausted, you can request an external review by an independent organization; that's a separate timeline with separate rules.

Escalate when you have to

If the insurer drags its feet, your state's Department of Insurance handles complaints and is usually responsive. The Centers for Medicare & Medicaid Services oversees plans on the federal marketplace. Both will follow up on an open complaint.