Your Insurer Said No: A Patient's Practical Roadmap for Appealing a Medical Necessity Denial

The letter arrives in the mail or appears in your patient portal, and the language is clinical but unmistakable: your insurer has determined that the treatment your physician prescribed, the diagnostic test your specialist ordered, or the referral your primary care doctor submitted does not meet the plan's definition of "medical necessity" and will not be covered. For many patients, this feels like a wall — immovable, technical, and backed by institutional authority.

It is not. It is, in fact, a starting line.

Federal and state laws grant insured Americans robust rights to challenge coverage denials. And the data is striking: according to findings published by the Kaiser Family Foundation, patients who appeal marketplace plan denials succeed in overturning them at rates exceeding 40 percent in many states. That figure climbs higher in certain categories of care. The problem is that most patients never appeal at all — often because they do not know they can, or because the process seems too complex to navigate without professional help.

This guide is designed to change that.

Understanding Why Denials Happen

Before mounting an appeal, it helps to understand the mechanics of why insurers deny claims. "Medical necessity" is the most common stated basis for denial, but the phrase carries a specific contractual meaning that varies by plan. Most insurers define a service as medically necessary when it is appropriate for the diagnosis or condition, consistent with accepted clinical standards, not primarily for the convenience of the patient or provider, and not experimental or investigational.

Denials frequently occur because:

• The insurer's clinical criteria differ from your physician's judgment. Insurers often use proprietary clinical guidelines — such as those published by Milliman or InterQual — that may set different thresholds than those recommended by specialty medical societies.
• Prior authorization was not obtained. Many plans require advance approval for certain procedures, imaging studies, or specialist visits. A failure in the administrative chain can trigger a denial even when the care itself would have been approved.
• The service falls outside the plan's formulary or network. Denials sometimes involve coding errors or network status issues rather than true clinical disputes.
• Documentation was incomplete. The treating physician's notes may not have included sufficient clinical detail to satisfy the insurer's review criteria.

Knowing the stated reason for your denial — which the insurer is legally required to provide — is the essential first step.

Your Legal Rights as an Insured Patient

The Affordable Care Act (ACA) significantly strengthened patient appeal rights for plans sold in the individual and small-group markets, as well as employer-sponsored plans subject to federal regulation. Key protections include:

• The right to an internal appeal. You must be given the opportunity to formally contest any denial within your insurer's own review process. The insurer must respond within specific timeframes — generally 30 days for non-urgent care and 72 hours for urgent situations.
• The right to an external review. If your internal appeal is unsuccessful, you have the right to have your case reviewed by an independent organization that has no financial relationship with your insurer. External reviewers are bound by clinical and legal standards, not the insurer's internal criteria.
• Access to the information used in the denial decision. You are entitled to request and receive all documents, guidelines, and clinical criteria the insurer relied upon when denying your claim.
• Continued coverage during appeals in certain circumstances. For ongoing treatments, you may be entitled to continued coverage during the appeals process.

Medicare enrollees have a parallel but distinct appeals system administered through CMS, with five levels of review available for Part A and Part B claim disputes.

Building Your Appeal: A Step-by-Step Approach

Step One: Request the Full Denial Explanation

Contact your insurer and request the complete Explanation of Benefits (EOB) and the specific clinical criteria used to evaluate your claim. Insurers are legally obligated to provide this information. Read the denial letter carefully to identify whether the basis is clinical (medical necessity), administrative (prior authorization), or contractual (plan exclusion), as each requires a different response.

Step Two: Engage Your Physician Immediately

Your treating physician is your most important ally. Ask them to write a detailed letter of medical necessity that directly addresses the specific criteria cited in the denial. This letter should:

• Reference your diagnosis using ICD-10 codes
• Cite peer-reviewed clinical literature supporting the recommended treatment
• Explain why alternative treatments the insurer may have suggested are not clinically appropriate for your specific case
• Document any prior treatments that were attempted and failed

A generic letter is less effective than one that directly responds to the insurer's stated rationale.

Step Three: Draft Your Internal Appeal Letter

Your own appeal letter should be concise, factual, and structured. A strong appeal letter includes:

• Your name, member ID, and claim number
• A clear statement that you are formally appealing the denial
• A brief summary of the treatment at issue and why it was prescribed
• A direct rebuttal of each reason cited in the denial
• References to your physician's supporting documentation
• Citations to clinical guidelines from recognized medical organizations (such as the American Diabetes Association, the American Cancer Society, or relevant specialty boards) that support the prescribed treatment
• A request for a peer-to-peer review between your physician and the insurer's medical reviewer

Sample opening language:

"I am writing to formally appeal the denial of coverage for [treatment/procedure], claim number [XXXXX], dated [date]. I believe this denial is inconsistent with both my plan's coverage terms and established clinical standards of care. Enclosed please find supporting documentation from my treating physician, [Dr. Name], along with relevant clinical literature."

Step Four: Request a Peer-to-Peer Review

Many patients are unaware that their physician can request a direct conversation with the insurer's medical reviewer — a process called a peer-to-peer review. This conversation frequently results in reversals, particularly when the insurer's reviewer is not a specialist in the relevant field. Ask your physician's office to initiate this request simultaneously with your written appeal.

Step Five: Escalate to External Review If Necessary

If your internal appeal is denied, do not stop. Request an independent external review immediately. External reviewers — accredited organizations approved by your state's insurance commissioner or CMS — apply objective clinical standards and overturn insurer decisions at meaningful rates. The external review process is typically free to the patient.

You can also file a complaint with your state's Department of Insurance, which has regulatory authority over insurers operating in your state. Many states have consumer assistance programs that can provide guidance or direct advocacy support at no cost.

When to Consider Additional Resources

For complex denials involving serious diagnoses — cancer treatment, mental health care, rare disease therapies — consider consulting a patient advocate. Independent patient advocates and healthcare attorneys can be retained to manage the appeals process on your behalf. Many patient advocacy organizations also offer free assistance for specific disease categories.

Additionally, if you believe your insurer is systematically denying a category of care in bad faith, your state insurance commissioner's office tracks complaint patterns and can initiate regulatory investigations.

The Broader Principle

An insurance denial is an administrative determination, not a clinical verdict. The physician who examined you, reviewed your history, and prescribed a course of treatment is in a fundamentally different position than a reviewer who evaluated your paperwork against a standardized checklist. The appeals process exists precisely because lawmakers recognized this imbalance.

Persistence, documentation, and a clear understanding of your rights are the tools that convert a denial letter into an approval. The process requires effort — but for the patients who engage it, the results demonstrate that effort is frequently rewarded.