How to Fight a Health Insurance Claim Denial (Your Appeal Rights, Step by Step)

Why claims get denied (and why many denials don't hold up)

Common denial reasons: "not medically necessary," coding errors, out-of-network charges, prior authorization missing, or the service being labeled experimental. A surprising share of denials are reversed on appeal — often because the first review was cursory or the paperwork was wrong.

Step 1 — Get the denial in writing and read it like a lawyer

Request the full explanation of benefits (EOB) and the denial letter with the specific reason and the policy language cited. Call and ask: "Please send me the clinical criteria you used and the name of the reviewer." You can't fight what you can't see.

Step 2 — File the internal appeal (you usually have 180 days)

Write a formal appeal letter: your name, policy number, claim number, the date of service, and a clear statement — "I am appealing the denial of claim [number] dated [date]." Attach: the denial letter, your doctor's letter of medical necessity (ask your doctor's office — they write these routinely), and any supporting records. Send it by a trackable method and keep copies of everything.

Step 3 — The external review: your strongest card

If the internal appeal fails, you have the right to an independent external review — a third-party medical reviewer with no ties to your insurer. Their decision is binding on the insurance company. File through your state's insurance department or the federal external review portal. This step reverses a large share of denials.

Step 4 — If they still won't pay

• State insurance commissioner complaint: regulators investigate patterns and individual complaints.
• Employer-plan? Different track: if your coverage is a self-funded employer plan (ERISA), appeals go through the US Department of Labor's process — ask HR for the plan's claims procedure.
• Negotiate the bill directly: in parallel, ask the provider for an itemized bill and a cash-pay discount — many will cut 20–40% for prompt payment.