How to Appeal a Health Insurance Claim Denial (Step-by-Step)

The First Step: Read Your EOB

Before you can appeal, you need to understand why your claim was denied. That answer is in your Explanation of Benefits (EOB) — the document your insurer sends after processing a claim.

Look for the "Reason Code" or "Denial Code" column on your EOB. It will show a code like "PR-96," "CO-4," or similar. These codes correspond to specific denial reasons — you can look them up at the Washington Publishing Company's code list or your insurer's website.

Common Denial Codes and What They Mean

CO-4: The service requires prior authorization
CO-22: The care may be covered by another plan (coordination of benefits issue)
CO-29: Claim filed too late (past timely filing deadline)
CO-50: Service not covered under the plan
CO-97: Payment included in another service's allowance
PR-96: Non-covered charge — excluded benefit
PR-204: Service not medically necessary per payer's determination

Your Legal Right to Appeal

The Affordable Care Act gives you the right to:

An internal appeal — the insurance company must review the denial again
An external review — an independent third party reviews if the internal appeal fails

Deadlines matter: you typically have 180 days from receiving your denial to file an internal appeal. Don't wait.

Step-by-Step Appeal Process

Step 1: Get All Your Documents

Your EOB showing the denial
The claim (usually from your provider)
Your insurance policy or summary plan description (SPD)
Any medical records relevant to the denied service

Step 2: Write Your Appeal Letter

Your appeal letter should include:

Your name, date of birth, member ID number
Claim number from the EOB
Date of service
A clear statement that you are appealing the denial
Why you believe the denial was wrong (cite your policy language or medical necessity)
Supporting documentation

Step 3: Get a Letter of Medical Necessity

If the denial was for "not medically necessary," ask your doctor to write a detailed Letter of Medical Necessity. This letter should explain:

Your diagnosis
Why the specific treatment/medication/service was required
What alternatives were tried or why alternatives are inappropriate
Citations to clinical guidelines or peer-reviewed literature if possible

Step 4: Submit and Track

Send your appeal via certified mail or through your insurer's online portal. Keep a copy of everything. Note the date submitted and the insurer's tracking number.

Step 5: Follow Up

Insurers have specific timeframes to respond:

Urgent/emergency: 72 hours
Standard (ongoing treatment): 30 days
Standard (after service): 60 days

If Your Internal Appeal Fails: External Review

If the insurer upholds the denial after your internal appeal, you can request an external review by an independent organization. The insurer must follow the external reviewer's decision.

Request external review within 4 months of your final internal denial. Your insurer must tell you how to request it in their denial letter.

Free Help Available

Your state insurance commissioner's office — can mediate disputes and check for insurer violations
Your HR department (if employer-sponsored insurance) — they often have a direct line to the insurer
Patient advocacy organizations — many disease-specific nonprofits have staff who help with appeals