How to Appeal a Denied Health Insurance Claim

A denial notice feels like a final answer. It isn't. Federal law gives you a structured right to challenge your insurer's decision, and a meaningful share of those challenges succeed.

Why Insurers Deny Claims in the First Place

Most denials aren't a verdict that the care you received was wrong or unnecessary. Many come down to process and paperwork.

Common denial reasons include:

• A missing or incomplete prior authorization (advance approval the insurer required before the service)
• A provider listed as out-of-network on the insurer's records
• A service coded as not medically necessary under the plan's criteria
• A straightforward billing or coding error by the provider's office

That last one is more common than people expect. A single wrong digit in a procedure code can trigger a denial that has nothing to do with whether the care was appropriate.

The reason on your denial matters because the strategy for pushing back differs by type. A coding error gets fixed at the provider's billing office. A medical necessity denial needs clinical documentation. Know your denial reason before you do anything else.

How to Read Your Denial Letter and EOB

You likely have two documents: a denial letter from your insurer, and an Explanation of Benefits (EOB). Together, they give you everything you need to start an appeal.

Insurers are required to provide a written denial notice that states the specific reason for the denial, the plan provision the insurer relied on, and instructions for how to appeal. If your letter doesn't include all three, call your insurer and ask for a written explanation that does.

The EOB is not a bill. It's a summary showing what your provider billed, what the insurer paid, and what the insurer says you owe. Reading the EOB alongside the denial letter often reveals a mismatch — for example, the provider billed under one code, but the insurer processed it under another.

A few things to look for on your EOB:

• Remark codes or reason codes — short codes (like CO-4 or PR-96) that explain how each charge was processed. Your insurer's EOB should include a legend or key.
• "Patient responsibility" vs. "plan paid", if the plan paid $0, that's where to focus.
• Service date and provider name, confirm these match what actually happened. Errors here can cause denials.

Keep both documents. You'll reference them throughout the appeals process.

The Internal Appeal: Your First Formal Step

An internal appeal is a formal request for your insurer to reconsider its decision. Under the Affordable Care Act, most health plans must allow at least one internal appeal, and insurers must decide urgent-care appeals within 72 hours and standard appeals within 30 days.

Watch the deadline. Many plans require you to file within 180 days of the denial. Missing that window can forfeit your right to appeal entirely. Check your denial letter or plan documents for the exact timeframe, as it varies.

A bare-bones "I disagree with this denial" letter rarely works. A strong internal appeal includes:

1. A letter of medical necessity from your treating provider, written specifically to counter the insurer's stated denial reason, not a generic note. Ask your provider's office to reference the insurer's language directly and cite relevant clinical guidelines.
2. Copies of relevant clinical records, visit notes, test results, or referral letters that support the medical case.
3. A written reference to the denial reason, state the exact reason from the denial letter and explain why it doesn't apply or is based on incorrect information.
4. Your denial letter and EOB, attach copies so everything is in one place.

Send everything by certified mail or through the insurer's secure online portal, and save confirmation of receipt.

External Review: An Independent Second Opinion

If your internal appeal comes back denied, the process doesn't stop there. Federal law gives you the right to an external review by an organization with no financial connection to your insurer. Critically, the insurer must accept and follow that external reviewer's decision.

Most states require you to request external review within 60 days of the final internal denial. The ACA sets a federal floor for this right for plans that don't have their own compliant state process, so it applies broadly, though some employer self-funded plans have different rules. Check your denial letter; it's required to include instructions for requesting external review.

In urgent situations where waiting would seriously jeopardize your health, you can skip straight to external review without going through the internal appeal first.

External review has a real track record of overturning insurer decisions, particularly for medical necessity denials. The clinical documentation that supported your internal appeal (especially your provider's letter of medical necessity) carries weight here too.

When to Ask Your State Insurance Commissioner for Help

Your state insurance department is a parallel resource, not a last resort. Every state has an insurance commissioner that handles consumer complaints about health plan denials and can intervene or escalate on your behalf.

Filing a complaint is free. It does not affect your right to continue appealing through your insurer, and it doesn't commit you to any particular outcome. In practice, a complaint filing sometimes prompts an insurer to take a closer look at a stalled appeal.

State departments are especially useful when:

• Your appeal has been pending longer than the required response window
• You believe the insurer isn't following its own plan documents
• You have a grandfathered or state-regulated plan that may not fall under the federal external review process

Some states also operate their own external review programs with broader consumer protections than the federal baseline. Your state insurance department's website will tell you what's available in your state.

Practical Steps to Strengthen Any Appeal

Whatever stage you're at, these habits make the process more manageable.

Get your provider actively involved. A letter of medical necessity that directly quotes the insurer's denial language and points to published clinical guidelines is the most effective tool in a standard appeal. Your provider's billing staff may also be able to fix a coding error before you need to file a formal appeal at all.

Keep a written log of every call. Note the date, the name or ID number of the representative you spoke with, and a summary of what was said. If you need to escalate to a state complaint or external review, this record matters.

Ask about free advocacy help. Patient advocates at the hospital or clinic where you received care can often walk you through the appeal process at no charge. Nonprofit patient advocacy organizations also assist with appeals, your insurer or provider's office can point you toward local resources.

Request a peer-to-peer review if one is available. Some insurers allow your treating provider to speak directly with the insurer's medical reviewer. Ask your provider's office if this option exists for your denial. It's separate from the formal appeal and sometimes resolves the issue faster.

One denial, even one upheld on internal appeal, is not the end of the line.

Where to Go From Here

If you're trying to find a provider who can support your appeal with documentation, including a letter of medical necessity, search the ProviderQuoHealth directory to find verified clinicians in your area. If you need a primary care provider to help coordinate your care and communicate with your insurer, the primary care specialty page is a good starting point.

Your state insurance department's website is also worth bookmarking. Most have a dedicated consumer assistance page with complaint forms and appeal guides specific to your state's rules.

Important note

This article is for general information and is not medical advice. It is not a substitute for professional care from a licensed clinician. If you have a medical concern, talk to a healthcare provider. If you are experiencing a medical emergency, call 911 (in the U.S.) or your local emergency number.