A health insurance appeal is a formal request asking your insurance company to reconsider a decision to deny coverage or payment for a medical service. If your insurer refuses to cover a treatment, procedure, or prescription, you have the legal right to challenge that decision. Under the Affordable Care Act, every person with a health plan created after March 2010 has access to a standardized appeals process, regardless of which state they live in or what type of insurance they have.
Most people never use this right. In 2023, fewer than 1% of denied claims in ACA marketplace plans were appealed. But among those who did appeal, roughly 44% got their denial overturned. That gap between how few people appeal and how often appeals succeed suggests many people either don’t know the process exists or assume it won’t work.
Why Claims Get Denied
Before you can appeal, it helps to understand why your claim was denied in the first place. The two broadest categories are administrative errors and medical necessity disputes.
Administrative denials happen when something is wrong with the paperwork: a missing referral, an incorrect billing code, a lapsed prior authorization, or incomplete patient information. These are often fixable without a full appeal, sometimes with a phone call to your provider’s billing office to resubmit the claim correctly.
Medical necessity denials are more substantive. Your insurer is saying it doesn’t consider the treatment necessary for your condition based on the clinical evidence it reviewed. This is the type of denial that most often requires a formal appeal with supporting documentation from your doctor.
Your insurer is required to notify you in writing when it denies a claim, and that letter must explain the reason. Read it carefully. The reason for the denial determines what kind of evidence you’ll need to overturn it.
How the Internal Appeal Works
The first stage is called an internal appeal, meaning your insurance company reviews its own decision. There are a few key steps and deadlines built into this process.
To start, you submit a written appeal to your insurer. You can use the company’s own forms or simply write a letter that includes your name, claim number, and health insurance ID number. Along with this, you should include any additional information that supports your case. A letter from your doctor explaining why the treatment is medically necessary is one of the strongest pieces of evidence you can provide. Medical records, test results, and documentation of how your condition affects your daily functioning all strengthen the appeal.
The American Medical Association recommends that physician support letters include three things: the specific symptoms or findings, objective evidence of functional impairment, and an argument for why the proposed treatment will address the condition. If your doctor is willing to write this kind of letter, it carries significant weight.
Your insurer must complete its review within set timeframes. For services you haven’t received yet, the internal appeal must be resolved within 30 days. For services you’ve already received (where you’re seeking reimbursement), the deadline is 60 days.
Expedited Appeals for Urgent Situations
If waiting 30 or 60 days would seriously jeopardize your life, health, or ability to recover, you can request an expedited appeal. The standard for qualifying is that the normal timeline would put you at medical risk.
For an expedited internal appeal, your insurer must deliver a decision within 72 hours of receiving the request. In some cases, the initial response can be verbal, but it must be followed by a written notice within 48 hours. You don’t need to go through the standard internal process first if your situation is truly urgent.
What Happens If the Internal Appeal Fails
If your insurer upholds its denial after the internal review, you have the right to take your case outside the company entirely. This is called an external review, and it’s handled by an independent third party that has no financial connection to your insurer.
This is where the process gets powerful. The external reviewer examines your case from scratch and issues a binding decision. If the reviewer decides in your favor, your insurer is required by law to accept that decision and cover the service. There’s no further negotiation.
The cost to you is minimal. If your insurer participates in the federal external review process administered by the Department of Health and Human Services, there’s no charge. If the review is handled through a state process or an independent review organization contracted by your insurer, you may be charged up to $25, but no more.
In 2023, marketplace enrollees filed about 5,000 external appeals, representing just 3% of all internal appeals that were upheld. Like internal appeals, external reviews appear to be significantly underused.
Deadlines You Need to Know
Timing matters throughout this process. When your insurer first denies a claim, it must notify you within specific windows: 15 days for prior authorization requests, 30 days for services already received, and 72 hours for urgent care situations. Pay attention to the date on your denial letter, because your own deadlines run from there.
Your plan documents will specify how long you have to file an internal appeal after receiving a denial. Federal rules for Medicare managed care plans recently extended this window from 60 to 65 calendar days, effective January 2025. For employer-sponsored and marketplace plans, the filing window varies by plan but is commonly 180 days. Check your denial letter or your plan’s evidence of coverage document for the exact deadline that applies to you.
How to Build a Strong Appeal
The most effective appeals share a few characteristics. First, they directly address the reason the claim was denied. If your insurer said the treatment wasn’t medically necessary, your appeal should include clinical evidence showing that it is. If the denial was based on a coding error, your appeal should include the corrected information.
Gather as much supporting documentation as you can. This includes your medical records, imaging or lab results, notes from specialists, and any clinical guidelines or peer-reviewed evidence showing that the treatment is standard for your condition. Ask your doctor to write a letter that specifically responds to the insurer’s reasoning. A generic “I recommend this treatment” letter is less effective than one that explains, point by point, why the insurer’s rationale doesn’t apply to your situation.
Keep copies of everything you send and note the dates. If your insurer misses a response deadline, that information becomes relevant if the case moves to external review.
Getting Help With Your Appeal
You don’t have to navigate this alone. Every state has a Consumer Assistance Program that can help you understand your rights and even file an appeal on your behalf. These programs are free. Your state’s department of insurance can also intervene if your insurer isn’t following the rules.
If your case involves a large bill or a complex medical situation, a patient advocate or healthcare attorney may be worth consulting. But for many appeals, especially those involving straightforward medical necessity disputes or administrative errors, the combination of a well-written letter, your doctor’s support, and the right documentation is enough to get a denial reversed.