If your health insurance claim is denied, you have the right to challenge the decision, and the process is more structured — and more winnable — than most people realize. Read the denial notice carefully, compare it to your policy, file an internal appeal within the deadline, and if that fails, request an independent external review whose decision is binding on the insurer. Move quickly. The clock starts the day the denial arrives.
Start With the Denial Notice
Every insurer must send you a written explanation when it denies a claim, spelling out the specific reason in language you can actually understand.1Office of the Law Revision Counsel. 29 USC 1133 – Claims Procedure That notice is your roadmap. It tells you whether you’re dealing with a billing mistake, a coverage question, or a medical necessity dispute, and each of those calls for a different response.
Most denials cite one of a few reasons: lack of medical necessity, out-of-network provider, pre-authorization not obtained, or service not covered. If the explanation is vague or uses codes you don’t recognize, call the customer service number on the notice and ask for a plain-English breakdown. You’re entitled to that.
A surprising number of denials come from simple administrative errors rather than genuine coverage disputes. A wrong billing code, a transposed digit in your policy number, or a missing referral form can trigger an automatic rejection. Compare the denial against the original claim your provider submitted. If you spot a clerical mistake, your provider can often correct and resubmit the claim without a formal appeal.
Match the Denial Against Your Policy
If the denial isn’t a clerical error, pull up your actual policy document and read the relevant sections. You’re looking for a mismatch between what the insurer says your policy covers and what the policy actually says.
Focus on three areas. Pre-authorization requirements: some treatments are covered only if your provider gets advance approval. Network restrictions: many plans cover out-of-network care at a lower rate or not at all, so confirm whether your provider really is out of network. Benefit limits: some policies cap the number of visits, sessions, or dollar amounts for specific types of care.
Insurers sometimes deny claims for treatments they classify as “experimental” or “investigational.” These labels can be subjective. If your doctor can point to published clinical evidence or professional society guidelines supporting the treatment, that documentation may be enough to challenge the classification.
If the denied care is for mental health or substance use disorder treatment, federal parity law requires your plan to apply the same standards it uses for medical and surgical benefits. Stricter pre-authorization rules, tighter visit limits, or heavier cost-sharing on behavioral health are strong signals of a parity violation, and denials that violate parity rules are good candidates for appeal.
File an Internal Appeal
You have a legal right to appeal any denied claim, and the insurer must give you a full and fair review conducted by someone who was not involved in the original decision.2eCFR. 45 CFR 147.136 – Internal Claims and Appeals and External Review Processes The reviewer’s job evaluation and compensation cannot be tied to how often they uphold denials.
For group health plan claims, you have 180 days from the date you receive the denial to file your internal appeal.3eCFR. 29 CFR 2560.503-1 – Claims Procedure Don’t wait. Gathering records takes time, and missing this deadline forfeits your appeal right.
To file, complete the appeal form on your insurer’s website or write a letter that includes your name, claim number, and insurance ID. Attach everything that supports your case: medical records, a letter from your doctor explaining why the treatment was medically necessary, lab results, imaging reports, and the specific policy language you believe supports coverage. A strong doctor’s letter is often the single most persuasive piece of evidence. Ask your provider to address the insurer’s stated reason for denial directly and to cite clinical guidelines or peer-reviewed research where possible.
Once you submit, the insurer has a set amount of time to respond. For care you haven’t received yet, the deadline is 30 days. For services already provided, it’s 60 days.4CMS. Appealing Health Plan Decisions If your appeal succeeds, the insurer approves the treatment or issues payment. If denied again, the insurer must explain the decision in writing and tell you how to take the dispute further.
Ask for an Expedited Appeal If It’s Urgent
If you’re facing a medical emergency, or waiting through the standard 30- or 60-day timeline would seriously jeopardize your health, you can file an expedited appeal. The insurer must decide an urgent care appeal within 72 hours.3eCFR. 29 CFR 2560.503-1 – Claims Procedure A claim qualifies as urgent if delay could seriously threaten your life, health, or ability to regain normal function, or if a physician confirms the delay would leave you in severe pain that can’t be managed without the disputed treatment.
In urgent situations, you can also request an external review at the same time you file your internal appeal, instead of waiting for the internal process to finish.5HealthCare.gov. Internal Appeals That exception can save days or weeks when time matters most.
Keep Ongoing Treatment Going During the Appeal
If the denied claim involves an ongoing course of treatment that is being reduced or terminated, federal regulations require the insurer to continue providing that coverage while your appeal is pending.2eCFR. 45 CFR 147.136 – Internal Claims and Appeals and External Review Processes The insurer cannot cut off treatment mid-course without giving you advance notice and a chance for review. If you’re in the middle of chemotherapy, physical therapy, or another treatment plan where interruption could cause real harm and your insurer tries to stop coverage before your appeal is resolved, cite this requirement directly.
Request an External Review
If your internal appeal fails, the next step is an external review, where an independent third party evaluates the insurer’s decision. Every health insurer must offer access to this process.6HealthCare.gov. External Review The reviewer is a medical professional or other expert with no financial ties to your insurance company, and the insurer has no say in who conducts the review.
You must file your external review request within four months of receiving the final internal appeal denial.6HealthCare.gov. External Review You’ll complete a form from your insurer or your state’s insurance department and submit supporting documentation, including medical records and any expert opinions that strengthen your case. Standard reviews must be decided within 45 days. Expedited reviews for urgent medical situations must be completed within 72 hours or less.
The external review decision is legally binding on the insurer. If the independent reviewer overturns the denial, your insurer must provide the coverage or pay the claim without delay, even if it later seeks judicial review of the decision.2eCFR. 45 CFR 147.136 – Internal Claims and Appeals and External Review Processes You also keep the right to pursue other legal remedies if needed. External review costs little or nothing to file, so there is almost no reason to skip it.
Surprise Bills From Out-of-Network Providers
If the denied claim or a linked balance bill involves an out-of-network provider you didn’t choose, federal law may override the situation entirely. The No Surprises Act prohibits balance billing in three situations: emergency care at any facility regardless of network status, non-emergency care from an out-of-network provider at an in-network facility, and air ambulance services from out-of-network providers.7Office of the Law Revision Counsel. 42 USC 300gg-111 – Preventing Surprise Medical Bills
Under these protections, your cost-sharing (deductible, copay, coinsurance) must be calculated as if the provider were in-network, and those payments count toward your in-network deductible and out-of-pocket maximum. The insurer and the out-of-network provider work out the remaining payment through an independent dispute resolution process.8CMS. Overview of Rules and Fact Sheets If a denial or balance bill appears to violate these rules, cite the No Surprises Act directly in your appeal.
If You’re on Medicare
Original Medicare (Part A or Part B) uses a different appeals system, with five levels you must complete in order.9CMS. Original Medicare (Fee-for-Service) Appeals
- Level 1 is a redetermination by the Medicare Administrative Contractor that processed your claim. You have 120 days from the initial denial to file.10CMS. First Level of Appeal: Redetermination by a Medicare Contractor
- Level 2 is a fresh reconsideration by an independent Qualified Independent Contractor.
- Level 3 is a hearing before an Administrative Law Judge at the Office of Medicare Hearings and Appeals, available only if the amount in controversy is at least $200 for 2026.11Federal Register. Medicare Appeals Adjustment to the Amount in Controversy Threshold Amounts for 2026
- Level 4 is review by the Medicare Appeals Council.
- Level 5 is judicial review in federal district court, available if the amount in controversy reaches at least $1,960 for 2026.11Federal Register. Medicare Appeals Adjustment to the Amount in Controversy Threshold Amounts for 2026
The dollar thresholds for Levels 3 and 5 adjust every year, so confirm the current amounts before filing. Each level has its own deadline printed on the decision notice you receive.
File a Complaint With a Regulator
If internal and external reviews both fail, filing a complaint with a regulator adds pressure. State insurance departments oversee private health insurers and investigate consumer complaints about unfair claim handling. Employer-sponsored plans governed by federal law fall under the Department of Labor. Medicare and marketplace plan issues go to the Centers for Medicare and Medicaid Services.
A complaint typically involves a written submission with copies of the denial notice, your appeal records, and correspondence with the insurer. Many states offer online portals. A complaint may not reverse your denial by itself, but regulators can investigate and, if they find a pattern, impose penalties or require corrective action. At minimum, it builds a paper trail that signals you’re not going away.
Consider Legal Action
Legal action is a last resort. An attorney who specializes in insurance law can evaluate whether the denial violates federal or state regulations, breaches your policy contract, or amounts to bad faith. Many offer free initial consultations.
If your coverage comes through an employer, your plan is almost certainly governed by the Employee Retirement Income Security Act. ERISA requires you to exhaust all internal administrative remedies before filing suit in federal court. Courts dismiss cases that skip the appeals process, with narrow exceptions for situations where pursuing administrative remedies would be clearly futile or where misleading conduct by the insurer justifies equitable tolling.
ERISA also shapes what you can recover. Lawsuits under ERISA are generally limited to the benefits owed under the plan; punitive damages and emotional distress claims are typically off the table. Courts can award attorney’s fees if you achieve some degree of success on the merits, which makes it easier to find a lawyer willing to take the case.1Office of the Law Revision Counsel. 29 USC 1133 – Claims Procedure Litigation is slow and expensive, so weigh the potential recovery against the time and cost before committing.
Handle the Bill While You Appeal
Providers don’t always wait patiently for an appeal to play out, and unpaid balances can eventually go to collections. Call your provider’s billing department as soon as you get the denial and let them know you’ve filed an appeal. Many will place a hold on the balance or set up a payment plan rather than send the account to collections during an active dispute. Get any agreement to pause billing in writing.
If you have a health savings account, you can pay the disputed amount with HSA funds while the appeal is pending. If the appeal succeeds and the insurer reimburses you, you can redeposit those funds into your HSA.
Keep copies of everything: the original claim, the denial notice, your appeal letters, supporting medical records, and all correspondence with the insurer. If your case reaches an external review, an administrative complaint, or a courtroom, that paper trail is your strongest asset.