Medical Claim Denied: How to Appeal

A denial is the insurer refusing to pay — it is not a bill you automatically owe. The most common reasons are fixable without ever arguing clinical merits:

• Missing or expired prior authorization / pre-certification.
• Coding mismatch — the diagnosis code doesn't justify the procedure code.
• Service billed as out-of-network, or the provider's network status was stale.
• Coordination-of-benefits problem: the plan thinks another insurer is primary.
• Eligibility gap — the claim was processed against a terminated policy.
• Deemed "not medically necessary" or "experimental / investigational."
• Timely-filing failure by the provider (that one is not your bill to pay).

Before appealing, call the insurer and ask whether the claim can simply be reprocessed. Coding and eligibility errors are often fixed in one call with no formal appeal at all.

These timelines come from the federal appeals rules that apply to most non-grandfathered plans.^[1],[2] Self-funded employer plans follow the parallel ERISA claims procedure, which uses the same 180-day window.^[3]

Request these in writing before you argue anything:

• The Explanation of Benefits and the written denial notice with its reason code.
• The full claim file — federal rules entitle you to free copies of all documents, records, and criteria used to decide your claim.^[3]
• The specific clinical policy or medical-necessity criteria applied.
• Your Summary Plan Description or Evidence of Coverage.
• An itemized bill and the office notes from your provider.

File in writing even if the plan accepts phone appeals, and keep a log of every call: date, time, representative name, and reference number. Ask your provider's office for a peer-to-peer review — a physician-to-physician call that reverses many medical-necessity denials before the formal appeal is even decided.

Send by a method that produces proof of delivery, and copy the appeal to your employer's benefits administrator if the plan is employer-sponsored.

• Member name, member ID, group number, claim number, and dates of service.
• The exact denial reason quoted from the notice, with its code.
• One paragraph of facts: what happened, what was ordered, and why.
• The plan's own language: quote the coverage provision or clinical criterion and show how your case meets it.
• A letter of medical necessity from the treating physician, plus supporting records.
• Published guidelines or literature supporting the treatment, if it was called experimental.
• A clear ask: "Reverse the denial and process claim #X as an in-network covered service," and a request for the criteria used if it is upheld.

Keep it to two pages plus attachments. Reviewers work from a checklist — make each required element easy to find.

If the internal appeal fails, you can send the case to an Independent Review Organization. The reviewer has no relationship with your insurer, and the decision is binding on the plan.^[2] You generally have four months from the final internal denial to request it. Depending on your plan and state, the request goes to your state insurance department or to the federal HHS-administered process; the denial letter must tell you which and give you contact details.

External review covers medical-necessity, experimental/investigational, and rescission decisions. It does not cover purely contractual exclusions — for those, the fight is over plan language, not clinical evidence.

If waiting would seriously jeopardize your health or your ability to regain function, say the words "expedited appeal" and have the physician document urgency. The plan must decide within 72 hours, and you may run the internal and external reviews at the same time.^[1] For surprise-billing and No Surprises Act questions, the federal Help Desk is 1-800-985-3059.^[5]

Original Medicare uses a five-level appeal ladder beginning with redetermination by the Medicare Administrative Contractor, generally within 120 days of the Medicare Summary Notice.^[4] Medicare Advantage and Part D plans have their own reconsideration timelines, and Medicaid appeals run through your state agency with a right to a fair hearing. Deadlines are shorter than commercial plans — check the notice, not this table.