What should I do first when my claim is denied?

Read the denial notice to find the exact reason and the appeal deadline, then request your plan's medical policy and your claim file. Don't pay the bill yet — a denied claim is not a final bill.

How long do I have to appeal a denied claim?

Under federal rules you generally have at least 180 days from the denial to file an internal appeal. Some plans and states set different windows, so check your denial letter and your state's rules.

Is it worth appealing a health insurance denial?

Usually yes. Fewer than 1% of denied marketplace claims are appealed, but insurers overturn roughly 44% of internal appeals and about half of external reviews.

Home › Resources › Claim denied: what to do

Your health insurance claim was denied. Here's what to do next.

Last reviewed June 2026 · CareCost Appeals editorial team · Sources cited below

A denial feels final. It usually isn't. Insurers deny a large share of claims, but fewer than 1% of people ever appeal — even though appeals are overturned a striking amount of the time (see the numbers). Here's the exact process, in order.

1. Read the denial — find the reason and the deadline

Your denial notice (often an Explanation of Benefits, or EOB) must state why the claim was denied and how to appeal. Two things to pull out:

The exact denial reason — e.g. "not medically necessary," "prior authorization not obtained," "out of network," "experimental." This determines your strategy. See types of denials.
The appeal deadline — usually counted from the denial date. Federal rules give you at least 180 days for an internal appeal, but plans and states vary. See appeal deadlines.

Note whether it's a pre-service denial (prior authorization, before treatment) or post-service (after a claim) — the timelines differ.

2. Don't pay the bill yet

A denied claim is not a final bill. Paying it can be read as accepting the charge. Wait until the appeal is resolved, and ask the provider to hold the account in appeal status.

3. Get the two documents that win appeals

Your plan's medical policy for the service — the insurer's own written coverage criteria. The strongest appeals quote these criteria back and show you meet them. We index policies for major insurers.
Your claim file / records — call the number on your insurance card and request the claim file and the specific criteria they say you failed.

4. Build the evidence

Match your situation to the policy criteria with proof:

A letter of medical necessity from your treating physician.
Records of treatments already tried and failed (important for step therapy and prior-auth denials).
Published clinical evidence (e.g. specialty guidelines, peer-reviewed studies) supporting the treatment.

5. File the internal appeal

This is a formal written request asking the insurer to reverse its decision. A strong letter: cites the plan's own criteria, attaches the evidence, names the regulations the insurer must follow, and demands they either approve or identify the specific criterion you fail. Submit by fax and certified mail and keep the confirmations. If your situation is urgent, request an expedited review (often decided within 72 hours).

6. If the internal appeal is denied, request external review

An independent third party (an IRO) reviews your case, and their decision is binding on the insurer. External review is free or near-free and overturned about half the time. See internal vs. external review.

Let CareCost build the appeal for you

Enter your denial and we generate the formal appeal letter — citing your insurer's own policy, real verified clinical evidence, and your state's deadlines and rights — plus a letter of medical necessity for your doctor.

Start my appeal

One more thing: whether your plan follows state law or federal ERISA rules changes your options. Self-funded employer plans are governed by ERISA; individual, marketplace, and small-group plans are usually state-regulated. Your state appeal-rights page explains which applies.

Sources: U.S. Centers for Medicare & Medicaid Services and HealthCare.gov, appealing a health-plan decision; KFF, Claims denials and appeals in ACA marketplace plans; National Association of Insurance Commissioners, consumer appeal guidance.

This guide is general information, not legal or medical advice. See our methodology and editorial standards.