How to Appeal a Denied Health Insurance Claim

Why health insurance claims get denied

Most denials fall into a handful of buckets. Your denial letter is required to state the specific reason — find that paragraph first, because your entire appeal responds to it.

• Not medically necessary. The insurer decided the service wasn't required to diagnose or treat your condition. This is the most commonly appealed reason.
• Experimental or investigational. The treatment isn't yet in the insurer's approved guidelines.
• Out-of-network. The provider wasn't in your plan's network, or no prior authorization was obtained.
• Administrative errors. Wrong billing code, missing prior authorization, or a claim filed past the timely-filing window. These are often the easiest to overturn.
• Coverage exclusion. The plan documents exclude the service (e.g., cosmetic procedures). These are harder, but the exclusion language itself can be challenged.

The 5-step appeal process

1. Read your denial letter carefully. Federal law requires it to explain the reason for denial, the plan provisions it relied on, and how to appeal — including your deadlines. Save it; you'll attach a copy to everything you file.
2. File an internal appeal with your insurer. This is a formal request asking the company to reconsider its own decision. You generally have at least 180 days from receiving the denial to file. Send it in writing (portal, fax, or certified mail) and keep proof.
3. If denied again, request an external review. An independent third party reviews your case — and its decision is binding on the insurer. You generally have at least 4 months after the final internal denial to request it. For most private plans this goes through your state's insurance department (see the directory below).
4. Ask for expedited review if it's urgent. If waiting would jeopardize your health, both internal appeals and external reviews can be expedited — decisions in as little as 72 hours (internal) or faster (external).
5. File a complaint with your state's insurance department. Separately from your appeal, regulators track complaint patterns and can intervene. It costs nothing.

Deadlines you can't miss

Miss a deadline and you can lose the right to appeal entirely. These are the federal minimums that apply to most private plans under the Affordable Care Act — your plan may give you longer, so always check your denial letter.

What makes an appeal letter work

A vague angry paragraph gets ignored. A letter that works is structured, factual, and easy for a reviewer to process in minutes. Every effective appeal letter includes:

• Your full name, contact info, member ID, and claim number
• Date of service and the amount denied
• The denial reason in the insurer's own words, quoted from the letter
• A short factual background — what happened, when, and what your doctor recommended
• Why the service was medically necessary and covered under your plan
• A clear, explicit request: overturn the denial and process the claim for payment
• A copy of the denial letter attached as an enclosure

Never invent facts, never threaten, and never skip the proofreading — one wrong claim number can sink an otherwise solid appeal. If any key fact is missing, flag it clearly rather than guessing.

Appeal in your state: 50-state directory

For most private plans, external review is handled through your state's insurance department. Find yours below — each link goes to the official regulator site where you can file for external review or submit a complaint.

Links verified September 2026. If a link has moved, search your state's name + "department of insurance" — regulator sites redesign often.

Common questions