How to appeal a health insurance denial

Start by reading the denial reason, not just the outcome

Every denial letter states a reason, and that reason decides your entire strategy. In KFF's analysis of coded 2024 marketplace denials, the largest categories were "other" reasons (36%) and administrative issues (25%), with medical necessity accounting for only about 5% of coded denials. Most denials aren't really arguments about your medical condition. They're paperwork problems: a missing code, a form that didn't reach the right department, information the insurer says it never received.

That matters because a paperwork denial is often fixable with a phone call and a resubmission, while a medical-necessity denial requires your physician's involvement from the start. Read the letter twice before you do anything else, and call the number on it to ask, plainly, what specific information they say is missing.

Figure out which appeal path applies to you

The rules differ depending on how your coverage works, and the difference changes who reviews your external appeal and which laws apply.

• If your coverage is through an employer that self-funds its health plan, you're under ERISA. Internal appeal first, under 29 CFR 2560.503-1, then a federal external review through plan-contracted independent review organizations or the HHS-administered process. State insurance law doesn't apply here.
• If you bought an ACA marketplace plan, or your employer's plan is fully insured rather than self-funded, internal appeal comes first, then external review runs through your state's process instead of the federal one.
• Medicare Advantage works differently: five levels, and if the plan upholds its own denial, the case gets automatically forwarded to independent review. You don't have to request it. The full breakdown is in our Medicare Advantage appeal guide.
• Medicaid managed care gets one appeal to your managed care organization, which can sometimes be done orally, followed by a state fair hearing if that fails.

You can usually tell which category you're in from the denial notice itself or your insurance card. If you're not sure whether your employer's plan is self-funded, ask HR directly. It's a normal question and they should have the answer immediately.

Calendar every deadline the day the denial arrives

The deadline printed on your actual denial notice always overrides any general number below, including the ones in this table. Check it first.

If your situation is urgent, meaning the standard timeline would seriously jeopardize your life, health, or ability to regain maximum function, you can request expedited review at both the internal and external stage at the same time. Don't file one and wait for it to finish before starting the other. That's the mistake that costs people the most time.

One live issue as of mid-2026: the HHS-administered federal external review portal (run through Maximus) has had reported outages. If you're filing a federal external review and the portal isn't working, your fallback is the plan-contracted IRO route, or a complaint to the Department of Labor's Employee Benefits Security Administration at 1-866-444-3272.

Request your procedural rights before you write anything

This is the single move people skip that they shouldn't. With any ERISA or commercial appeal, you have the right to request, in writing, three things: the complete claim file, the specific internal clinical criteria or guideline the insurer used to deny you, and the identity and specialty of whoever reviewed the claim. All three are free. Ask for them the same day you file your appeal, not after.

Two things happen when you do this. First, you usually get the actual clinical policy the insurer is measuring you against, which tells you exactly what to argue against instead of guessing. Second, if the insurer misses its own deadlines or skips a procedural step, like using a reviewer who isn't a specialist in the relevant field, that failure can cost them their normal deferential standard of review. Courts and external reviewers sometimes treat a badly-run appeal process as "deemed exhaustion," meaning the case goes straight to independent review or de novo court review. Procedural failures are worth citing explicitly in your letter.

Build your argument on the plan's own words

Once you have the internal criteria document, the job is straightforward, even if it isn't easy: go through it line by line and show, with your medical records, that you meet each element. External reviewers decide cases against the plan's own published criteria, not against a general sense of fairness. An appeal that says "this should be covered" loses to an appeal that says "your own policy requires coverage when X, Y, and Z are met, and here is where my chart shows each one."

What actually goes in the letter

A complete appeal letter has a specific anatomy: your identifying information and a citation to the appeal procedure you're invoking, a clear one-paragraph statement of what you're asking for, the denial reason quoted back verbatim, a point-by-point rebuttal tied to the plan's criteria document, a letter from your treating physician covering necessity and any step-therapy history, supporting evidence from specialty-society guidelines or peer-reviewed literature, the procedural-rights requests from the step above, and a recital of your deadline. We cover this piece by piece, including exactly what the physician letter needs to say, in what to include in an insurance appeal letter.

One more thing worth doing on every appeal: send a copy to your state's Department of Insurance or Consumer Assistance Program. It's not a formal part of the process, but insurers behave differently when a regulator is watching the file.

If the internal appeal is denied, external review is next

A denial at the internal stage isn't the end. External review sends your case to an independent organization with no financial relationship to your insurer, and their decision is binding on the insurer, not just advisory. It only covers certain kinds of determinations (medical necessity, appropriateness, and experimental or investigational calls), and you have to have gone through the internal process first, unless the insurer's own procedural failures excuse that requirement. We walk through eligibility, the 4-month window, and the 72-hour expedited path in external review explained.

Where this doesn't work as well

Be honest with yourself about one category: if your plan flatly excludes an entire category of treatment by contract, like a plan that excludes weight-loss drugs altogether regardless of medical need, external review generally can't override that exclusion. It's a contract term, not a clinical judgment, and clinical review doesn't reach it. If that's your situation, your better options are checking whether a different diagnosis code changes the coverage picture, going directly to your employer's benefits team, or looking into manufacturer patient-assistance programs. Our GLP-1 denial guide covers this distinction in detail because it comes up constantly with Zepbound, Wegovy, and Mounjaro denials.