A denial letter arrives, the amount at the bottom is large, and the explanation is a code you have never seen. Most people assume the decision is final. It is not. When you appeal a denied health insurance claim, you are using a right that federal and state law guarantee you, and a meaningful share of appeals succeed.
Denials happen for ordinary reasons far more often than dramatic ones. A wrong digit in a diagnosis code, a missing prior authorization, a provider filed under the wrong tax ID, a service coded as cosmetic when it was reconstructive.
This guide walks through why claims get denied, the exact steps of an internal and external appeal, what to write, what deadlines apply, and what to do if the appeal does not go your way the first time.
First, Figure Out What Was Actually Denied
Before you write anything, separate three documents that people often confuse.
The explanation of benefits, or EOB, comes from your insurer and is not a bill. It shows what the provider charged, what the plan allowed, what it paid, and what it left to you. The denial letter or adverse benefit determination states the reason and your appeal rights. The provider bill comes from the hospital or practice and asks you for money.
Read the EOB and the denial letter together. If you are unsure how to interpret the columns, our walkthrough on how to read a medical bill and EOB maps each line to what it means. Note the claim number, the date of service, the CPT and diagnosis codes, and the denial reason code. You will need all of them.
Why Health Insurance Claims Get Denied
Understanding the category of denial tells you what kind of appeal to write.
Administrative and Coding Denials
These are the most common and the easiest to fix. A missing referral, an expired member ID, a typo in the date of birth, a provider billing under a group number the plan does not recognize, or a diagnosis code that does not support the procedure code. Often a phone call to the billing office solves it before a formal appeal is needed.
Medical Necessity Denials
The plan agrees the service is covered in principle but says this particular patient did not need it, or needed something cheaper first. These require clinical documentation from your provider, not just a letter from you.
Prior Authorization Denials
The service required advance approval and did not get it, or the approval expired before the service happened. These are frustrating because the care already occurred, but plans frequently reverse them when the provider shows the request was submitted or the situation was urgent.
Network and Benefit Denials
The provider was out of network, the benefit is excluded from your plan entirely, or you had not met your deductible. Exclusion denials are the hardest to overturn. Out-of-network denials sometimes are not valid at all, particularly for emergency care, which is where federal surprise billing protections come in. Our guide to surprise medical bills covers those rules.
Formulary and Step Therapy Denials
A prescription is not on the plan’s list, or the plan wants you to try a preferred drug first. These have their own appeal track, usually called a coverage determination or exception request. If cost is the underlying problem, our tips on how to lower prescription drug costs may resolve it faster than an appeal.
The Two Levels of Appeal
Most plans give you an internal appeal, decided by the insurer, followed by an external review decided by an independent third party. The external decision is binding on the plan.
| Stage | Who Decides | Typical Deadline to File | Typical Decision Time | Outcome |
|---|---|---|---|---|
| Informal correction | Provider billing office and insurer | Anytime | Days to a few weeks | Claim reprocessed if coding was wrong |
| Internal appeal, level one | Your insurance company | Often 180 days from denial | Often 30 days for services not yet received, 60 days for services already received | Upheld or overturned |
| Internal appeal, level two | Insurer, different reviewer | Set by plan documents | Similar to level one | Available in some plans only |
| External review | Independent review organization | Often 4 months after final internal denial | Often 45 days | Binding on the plan |
| Expedited review | Insurer or independent reviewer | Immediately, for urgent care | Often 72 hours or less | Used when delay would seriously jeopardize health |
Deadlines and timelines differ by plan type, employer arrangement, and state. Self-funded employer plans follow federal rules; fully insured plans also follow state law. Your denial letter states the deadlines that apply to you, and those control. Confirm them with your plan rather than relying on general figures.
How to Appeal a Denied Health Insurance Claim, Step by Step
- Call the insurer and ask for the specific denial reason in plain language. Write down the representative’s name, the date, the time, and a reference number for the call. Ask whether the denial is administrative or clinical, because that determines everything else.
- Call the provider’s billing office next. Ask them to review the codes submitted. If a modifier is missing or the diagnosis does not match the procedure, they can often correct and resubmit, which is faster than an appeal.
- Request your plan documents. Ask for the summary plan description and the specific medical policy or clinical criteria the insurer used. You are entitled to the criteria that produced the denial, and it tells you exactly what your appeal must address.
- Gather your evidence. Collect the EOB, the denial letter, the itemized bill, relevant office notes, imaging reports, prior treatment history, and any prior authorization confirmations.
- Ask your doctor for a letter of medical necessity. This is the single most important document in a clinical appeal. It should state the diagnosis, what was tried before, why alternatives were unsuitable, and why the service met the plan’s own criteria.
- Write the appeal letter. Keep it short, factual, and organized around the plan’s criteria rather than around how you feel.
- Submit before the deadline and keep proof. Use the method the denial letter specifies. Send by a trackable method or through the member portal, and save the confirmation.
- Follow up every two weeks. Log every call. If the insurer misses its own decision deadline, say so in writing.
- Request external review if the internal appeal fails. The final internal denial letter must tell you how. An independent organization then reviews the file, and its decision binds the plan.
What to Put in the Appeal Letter
A strong appeal letter is usually one page. Include these elements in this order.
- Your name, member ID, group number, claim number, and dates of service at the top.
- A single opening sentence stating that you are formally appealing the denial dated whatever the date was.
- The denial reason exactly as the insurer stated it, quoted back.
- Two to four factual sentences explaining why that reason is incorrect or does not apply.
- A reference to the plan’s own coverage criteria and how your situation meets them.
- A numbered list of enclosed documents.
- A clear request: reprocess the claim and pay it, or approve the service.
Avoid long emotional narratives. Reviewers work from criteria and documentation. Emotion does not move a criteria-based decision, but a physician’s note that directly addresses the criteria often does.
Special Situations
Urgent and Expedited Appeals
If waiting for a standard decision would seriously jeopardize your health or your ability to regain function, you can request an expedited appeal. These are decided in a very short window, often within 72 hours. You can usually request an expedited external review at the same time as the internal one rather than waiting.
Ongoing Treatment Already Approved
If a plan tries to reduce or end treatment it previously approved, you generally have the right to continued coverage during the appeal in many plan types. Ask about this specifically, because it is rarely volunteered.
Medicare Appeals
Medicare uses its own multi-level process, and it differs depending on whether you have Original Medicare, a Medicare Advantage plan, or Part D. Timelines and forms are not the same as commercial insurance. If you are still deciding between the two paths, our comparison of Medicare Advantage vs Original Medicare explains how appeal rights differ. Details for each level are published at Medicare.gov.
Employer Plans
If your coverage comes through an employer, your HR or benefits team can sometimes escalate internally in ways an individual member cannot. Large employers that self-fund their plans have real leverage with the administrator. Ask.
Mistakes That Sink Otherwise Winnable Appeals
- Missing the filing deadline, which is the most common fatal error.
- Appealing verbally only and having no written record.
- Writing about financial hardship instead of medical necessity, when necessity is the stated denial reason.
- Not requesting the clinical criteria, and therefore arguing against a reason the insurer did not give.
- Letting the provider send a bill to collections while the appeal is pending instead of telling the billing office the claim is under appeal.
- Stopping after the first internal denial without using the external review right.
Who Can Help You for Free
You do not have to do this alone, and you should not pay for help before trying free channels.
- Your state department of insurance or insurance commissioner, which handles complaints and can force a response from a fully insured plan.
- Your state’s consumer assistance program, where one exists, which helps consumers file appeals directly.
- The hospital’s patient advocate or financial counselor, who often knows exactly which code caused the problem.
- Your employer’s benefits administrator, for group coverage.
- Disease-specific nonprofit organizations, many of which have case managers who handle insurance appeals routinely.
General consumer information about internal and external appeals is published at HealthCare.gov, including what your denial letter is required to tell you.
What Happens After You Win
If the appeal is overturned, the insurer reprocesses the claim and issues a corrected EOB. Check that new EOB carefully against the original bill. Then contact the provider to confirm they received the payment and to ask for a corrected statement.
If you already paid the bill out of pocket before the appeal succeeded, request a refund in writing from the provider. This is common and legitimate, but it rarely happens automatically.
If the appeal is upheld and you have exhausted external review, you still have options: ask the provider for an itemized bill and review it for errors, request financial assistance or charity care, and negotiate a payment plan. Many hospitals have written assistance policies that are not advertised at the front desk.
Frequently Asked Questions
How long do I have to appeal a denied health insurance claim?
Many plans allow 180 days from the date of the denial notice for an internal appeal, and roughly four months after a final internal denial to request external review. Your denial letter states the deadlines that govern your specific plan, and those override any general figure. File early rather than at the edge of the window.
What are the odds an appeal succeeds?
Outcomes vary widely by denial type and plan, but a substantial share of appealed claims are reversed, especially administrative and coding denials that get corrected on resubmission. Clinical denials succeed more often when a physician submits documentation directly addressing the plan’s own coverage criteria rather than a general letter of support.
Do I need a lawyer to appeal?
Usually not. Most appeals are resolved through the insurer’s own process using documents you and your doctor can assemble. Free help is available from state insurance departments, consumer assistance programs, and hospital patient advocates. Legal help becomes more relevant for very large amounts or after external review has been exhausted.
Can my doctor file the appeal for me?
Often yes. Providers can appeal on your behalf, and many billing departments do this routinely, particularly for prior authorization and medical necessity denials. You may need to sign an authorized representative form. Confirm in writing who is filing so an appeal does not fall between you and the office.
Should I pay the bill while the appeal is pending?
Tell the provider’s billing office in writing that the claim is under appeal and ask them to hold the account. Many will pause collection activity. If you do choose to pay to protect your credit, keep the receipt, because you can request a refund if the appeal is later decided in your favor.
The Bottom Line
A denial is an opening position, not a verdict. The system expects you to push back, and it builds in two formal levels of review precisely because first decisions are often wrong.
Start by identifying whether the problem is a code or a clinical judgment, because that determines everything you do next. Get the plan’s own criteria in writing, ask your doctor for a letter that addresses those criteria directly, and file before the deadline with proof of submission.
Keep a simple log of every call, every name, and every date. That log is what turns a frustrating process into a manageable one, and it is often what convinces an insurer to correct a mistake before an independent reviewer does it for them.
This article is for general information only and is not medical, legal, or financial advice. Costs, coverage rules, and eligibility change over time and vary by state, insurer, and provider. Always confirm details with a licensed professional or your plan administrator before making a decision.
