Health Insurance Claim Denied? Internal Appeals and External Review Explained

A denied health insurance claim is not always the final word. Denials happen for many reasons: coding errors, missing prior authorization, out-of-network care, lack of medical-necessity documentation, eligibility problems, benefit exclusions or disputes over whether a treatment is experimental.

The best appeal is not a generic complaint. It directly addresses the denial reason with the plan language, medical records and facts needed to reverse that specific decision.

First: identify exactly what was denied

Start with the Explanation of Benefits (EOB) and the formal adverse-benefit-determination letter. They should tell you what the plan received, what it paid, what it denied and why. Common categories include:

• Service is not a covered benefit.
• Prior authorization was required or not obtained.
• Provider was out of network.
• Treatment was considered not medically necessary.
• Treatment was considered experimental or investigational.
• Claim was filed too late.
• Patient was considered ineligible on the date of service.
• Claim code, diagnosis code or billing information was incomplete.

Internal appeal: the plan reviews its own decision

HealthCare.gov states that consumers generally have 180 days (six months) after receiving a denial notice to file an internal appeal. The appeal can include forms required by the insurer or a written request with identifying claim information, plus medical and factual evidence.

Build the appeal around the denial code

If the denial says “not medically necessary,” ask the plan for the clinical criteria used and have the treating clinician explain how the patient meets them. If it says “experimental,” provide peer-reviewed evidence, specialty-society guidance and the clinician’s rationale. If it says “no authorization,” verify whether authorization was actually required, whether the provider requested it and whether emergency or continuity-of-care rules apply.

Ask for the governing plan document

An EOB summary is not the whole contract. Employer plans may have a Summary Plan Description and other governing documents; individual plans have certificates/policies and benefit schedules. The appeal should cite the actual coverage rule where possible.

Internal appeal evidence checklist

• Copy of the EOB and denial letter.
• Claim number, member ID and dates of service.
• Relevant pages from the policy or plan document.
• Doctor’s letter explaining diagnosis, medical necessity and alternatives tried.
• Clinical notes, test results and prior treatment history.
• Prior-authorization records and reference numbers.
• Relevant guidelines or peer-reviewed evidence when appropriate.
• Timeline of calls with names, dates and reference numbers.
• Proof of timely filing and delivery of the appeal.

External review: an independent third party

If the plan upholds a qualifying denial, federal consumer-protection standards provide access to external review. HealthCare.gov describes external review as a process where an independent reviewer—not the insurer—decides whether the denial should stand. If the external reviewer overturns the decision, the insurer is required to accept it under the applicable process.

External review commonly applies to denials involving medical judgment, experimental/investigational treatment and certain rescissions. Not every administrative or contract dispute is eligible.

How long does external review take?

HealthCare.gov states that a standard external review is decided as soon as possible, no later than 45 days after the request is received. Expedited external review is decided as soon as possible and generally no later than 72 hours, subject to medical urgency and the applicable process.

Urgent cases can move faster

If waiting for the normal appeal process could seriously jeopardize life or the ability to regain maximum function, expedited procedures can apply. HealthCare.gov notes that an external review can sometimes proceed before the internal appeal is fully completed in urgent circumstances.

For an immediate medical emergency, focus first on getting appropriate care. Appeal rights should not delay emergency treatment.

State vs. federal external review

The route depends on your state and type of health plan. Some states operate external-review systems that meet or exceed federal standards. In other situations HHS-administered or other federal processes apply. Self-funded employer plans can involve federal ERISA rules rather than ordinary state insurance regulation.

The final denial should tell you where to request external review. If it is unclear, contact the plan, your state insurance department or a Consumer Assistance Program.

Do not confuse a claim appeal with a Marketplace eligibility appeal

A health-plan claim appeal asks whether the insurer or plan should cover/pay a medical service. A Marketplace appeal addresses decisions such as eligibility for coverage or premium tax credits. They are different processes.

A model appeal structure

1. Identify the denial. Claim number, service, date and denial reason.
2. State the requested remedy. Ask the plan to cover or reprocess the specified service.
3. Cite the plan terms. Quote only the relevant coverage/medical-necessity language.
4. Explain the facts. Why the patient satisfies the requirement.
5. Attach evidence. Medical records, letters and prior-authorization documentation.
6. Request expedited handling if justified.
7. Keep proof of submission.

If the denial is a billing error rather than a coverage dispute

Some “denials” can be corrected through claim resubmission instead of a formal medical appeal—for example, an incorrect patient ID, duplicate claim, coding mismatch or missing modifier. Ask the provider’s billing office and plan whether a corrected claim should be submitted first.

Reviewed October 5, 2026. Health-plan appeal routes vary by plan type, state and denial reason. Always use the deadline and instructions on the current denial notice.