How to appeal a denied health insurance claim

Those numbers come from KFF's analysis of 2023 HealthCare.gov marketplace data. The process is more winnable than most people think — but you need to follow it exactly.

Step 1 — Read the denial letter carefully

The Explanation of Benefits (EOB) or denial letter must include:

• The specific reason for denial (with CARC/RARC codes)
• The appeal deadline (usually 180 days from denial)
• Instructions for filing an internal appeal
• Your right to an external review after exhausting internal appeals

Common denial reasons: not medically necessary, experimental/investigational,out of network, pre-authorisation missing, incorrect coding,not covered under the plan.

Step 2 — Understand your plan

Get your plan's Summary of Benefits and Coverage (SBC) and the full Evidence of Coverage (EOC) or Certificate of Insurance. These are the contracts that bind the insurer. Find the specific language that shows the service should be covered. Screenshot or print the relevant page.

Step 3 — Gather supporting documentation

For a medical-necessity denial, assemble:

• A letter of medical necessity from your doctor
• Relevant clinical guidelines (e.g. NCCN, ACOG, or your specialty society) supporting the treatment
• Peer-reviewed studies if the insurer claims the treatment is experimental
• Your full medical records for the relevant episode

Step 4 — Write the internal appeal

The appeal letter should include:

1. Your name, DOB, member ID, claim number, date of service
2. The specific denial reason you're contesting, quoted from the EOB
3. A clear, calm statement of why the denial is wrong
4. A quote from your plan document showing coverage
5. Supporting evidence (attach, don't paste into the body)
6. A clear ask: “I request that this denial be reversed and the claim paid.”

Send via certified mail or the insurer's online portal — keep the receipt and tracking. Most insurers must decide within 30 days for pre-service denials and 60 days for post-service denials.

Step 5 — If denied again, request external review

After you exhaust the internal appeal process (usually one or two rounds), you are entitled to an external review by an Independent Review Organisation (IRO). This is a doctor or panel unaffiliated with the insurer. Their decision is binding on the insurer. File within 4 months of the final internal denial.

For ACA marketplace plans, the HHS-administered external review is the default unless your state runs its own. Start at HealthCare.gov.

Step 6 — Expedited appeals for urgent care

If a delay would seriously jeopardise your health, ask for an expedited appeal. The insurer must decide within 72 hours, and you can file internal and external appeals simultaneously.

When to bring in help

For denials over about $5,000, or for repeat denials of the same treatment, a patient advocate, a billing attorney, or your state's Consumer Assistance Program can help. Many operate free of charge.

This guide is decision-support content, not legal or medical advice. Appeal deadlines are strict — if in doubt, call your insurer or a licensed advocate immediately.