How to appeal a health insurance denial, step by step

By MedAppealsRN · Updated October 1, 2026 · 8 minute read
Created by a registered nurse who works firsthand with prior authorizations, appeals, and denials.

A denial letter feels final. It isn't. You have a legal right to ask your health plan to look again, and many people who appeal get the decision reversed. This guide walks through what to do, in order, starting today.

Why it is worth appealing

Very few people appeal. In federal data on HealthCare.gov plans, consumers appealed fewer than 1% of denied in-network claims in 2024. Yet when people do appeal, a meaningful share win. For prior authorization denials in 2025, plans reported overturning about two thirds of appealed denials in Medicare Advantage, and over 40% in Medicaid managed care and the ACA Marketplace.

In other words, the plan's first answer is often not its last one. Many denials come from missing paperwork, coding issues, or a reviewer who did not see the full picture. An appeal is your chance to fill in that picture.

Step 1: Read the denial letter closely

Your denial letter (sometimes called an adverse benefit determination or an Explanation of Benefits) contains almost everything you need. Look for:

• The reason for the denial. Common reasons are "not medically necessary," "no prior authorization," "out of network," and "experimental or investigational." Your appeal has to answer this specific reason.
• Your deadline to appeal. It is usually stated near the end, along with how to file.
• The claim or reference number. Put it on every page you send.
• Where to send your appeal, including the mailing address, fax number, or online portal.
• Whether your situation is urgent. The letter should explain how to ask for a faster decision.

Keep the original letter somewhere safe. You will include a copy with your appeal.

Step 2: Find your deadline and put it on your calendar

Deadlines depend on where your coverage comes from. The date printed on your denial letter is the one that counts, but these are the general federal rules:

Don't wait until the last week. Starting early gives your doctor time to write a letter and gives you time to gather records.

Step 3: Ask for your claim file and the rules the plan used

You can ask the plan for a free copy of the documents and the clinical criteria it used to deny your claim. This tells you exactly what the reviewer was looking for, so your appeal can respond point by point. Call the member services number on your insurance card, ask for "the claim file and the criteria used for this decision," and write down the date, the name of the person you spoke with, and any reference number.

Step 4: Get your doctor involved

A letter from your doctor is often the strongest part of an appeal, especially for "not medically necessary" denials. Ask your doctor's office for a letter of medical necessity that explains:

• Your diagnosis and how it affects your daily life
• Treatments you have already tried and what happened
• Why this specific service is needed now
• What is likely to happen without it
• Any clinical guidelines or studies that support it

You can also ask whether your doctor will request a peer-to-peer review, a phone call with the plan's reviewing clinician. These calls sometimes resolve a denial before a written appeal is even decided.

Step 5: Write your appeal letter

A good appeal letter is short, specific, and polite. It should include:

1. Your name, member ID, and claim or reference number
2. A clear statement that you are requesting an appeal (or a "reconsideration" for Medicare Advantage)
3. The service that was denied and the date of the denial letter
4. A direct response to the plan's stated reason
5. A request for the criteria the plan used and, if relevant, a peer-to-peer review
6. A list of what you are enclosing

Stick to facts. You don't need legal language, and you don't need to be long. Two pages that answer the denial reason clearly will do more than ten pages of background.

Step 6: Send it in a way you can prove

• Send by certified mail with return receipt, by fax with a confirmation page, or through the plan's online portal with a screenshot of the confirmation.
• Write your member ID and claim number on every page.
• Keep a complete copy of everything you send.
• About a week later, call to confirm the plan received your appeal, and ask when to expect a decision.

Step 7: Ask for a faster decision if waiting could harm you

If waiting the standard time could seriously jeopardize your life, health, or ability to regain function, ask for an expedited appeal. Plans must decide urgent appeals within 72 hours. A short statement from your doctor that the situation is urgent makes approval of a fast appeal much more likely.

Step 8: If the plan still says no, go outside the plan

Employer plans and plans you bought yourself

After a final internal denial, you can usually request an external review by an independent reviewer who does not work for your plan. You generally have 4 months from the final denial to ask. Standard external reviews must be decided within 45 days, and expedited ones within 72 hours. Your final denial letter explains where to send the request. Some older "grandfathered" plans may not offer this, so check your plan documents.

Medicare Advantage

If your Medicare Advantage plan upholds its denial, it must send your case automatically to an Independent Review Entity for the next level of review. You don't have to file anything for that step, but you can send additional information to support your case. The notice you receive explains what happens next and any later deadlines.

Where to get free help

• Your state's insurance department or consumer assistance program can answer questions about appeals and external review.
• If you have Medicare, your State Health Insurance Assistance Program (SHIP) offers free, unbiased counseling.
• Your doctor's office often has staff who handle prior authorizations and appeals every day.

Common questions

Does it cost anything to appeal?

Filing an appeal with your health plan does not cost anything. External reviews are usually free or very low cost for consumers.

Can I appeal a bill for care I already received?

Yes. Post-service denials can be appealed the same way. Your letter should ask the plan to reprocess the claim and pay it under your benefits.

What if I missed the deadline?

Call your plan anyway and ask whether they accept late appeals for good cause, such as a hospital stay or not receiving the letter. Then ask your state insurance department about other options.

This guide is general information, not legal or medical advice. Rules vary by plan and state, and the deadlines on your own denial letter control. MedAppealsRN is not affiliated with any insurer.