Quick Answer
A "not medically necessary" denial means your insurer claims the requested service isn't medically required. Appeal it within 180 days by submitting: (1) clinical-practice guidelines from your specialty society, (2) the FDA-approved indication via DailyMed if a drug is involved, (3) a treating-physician letter of medical necessity, and (4) any CMS National or Local Coverage Determination (NCD/LCD) that applies. Most medical-necessity denials are overturned on internal or external review when properly supported. AppealArmor generates the full appeal in 60 seconds, free.
Last updated: 2026-05-25 · Source: AppealArmor · About the authors
Insurance Denial Help
Medical necessity denials are the most common reason insurers reject claims. But fewer than 1 in 500 denied claims are ever appealed — and independent reviews overturn denials at significant rates. You have the right to fight back.
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"Medical necessity" is the standard insurers use to determine whether a treatment or service is required to diagnose or treat your condition. When your claim is denied as "not medically necessary," your insurer is saying the service does not meet their internal clinical criteria.
This is the single most common denial reason in the United States. But here is what insurers do not tell you: their criteria often conflict with your treating physician's clinical judgment and with published, evidence-based medical guidelines.
The physician reviewing your claim on behalf of the insurer has never examined you, has no doctor-patient relationship with you, and is paid by the company that profits from denying your claim. Courts have increasingly recognized this conflict in ERISA litigation.
Common treatments denied for medical necessity include MRIs, CT scans, surgical procedures, physical therapy beyond initial sessions, specialist referrals, prescription medications, mental health treatment, and durable medical equipment.
Sources: Kaiser Family Foundation (2023 Marketplace Transparency), HHS Office of Inspector General, state insurance department annual reports
Take a photo or upload the PDF. Our AI extracts every detail: insurer name, claim number, denial reason codes, service dates, diagnosis codes, procedure codes, and appeal deadlines. No forms to fill out.
AppealArmor searches CMS National Coverage Determinations (NCDs), Local Coverage Determinations (LCDs), insurer-specific clinical guidelines, state insurance regulations, federal law (42 USC 300gg-19, ERISA 503), and peer-reviewed medical literature to build the strongest possible argument.
You receive a professionally written appeal letter, a state regulatory complaint (for additional pressure), a list of strategic CC recipients including your state insurance commissioner, and step-by-step mailing instructions. Ready to send in minutes.
Guarantees your right to internal appeal and external independent review. Requires insurers to use evidence-based clinical criteria and to provide you with the specific reason for denial, the clinical guidelines used, and information about how to appeal.
For employer-sponsored plans: requires "full and fair review" of denied claims. Plans must provide specific denial reasons, give you access to your claim file, and allow you to submit additional evidence during the appeal.
If your internal appeal is denied, you have the right to an external review by an independent physician who was not involved in the original decision. HHS OIG and state DOI annual reports consistently show external reviewers overturn insurer denials at significant rates — often 40% or more depending on the state and denial category.
Most states have additional protections, including independent medical review boards, expedited appeal timelines for urgent cases, and the authority for your state insurance commissioner to investigate patterns of improper denials.
It means the insurer's reviewing physician determined the service does not meet the plan's clinical criteria for your condition. Critically, this reviewer has never examined you and may be applying guidelines that differ from current evidence-based standards. Your treating physician's recommendation is not automatically overridden by this determination, and you have the legal right to challenge it.
The strongest medical necessity appeals include: (1) a detailed letter from your treating physician explaining why the treatment is required, (2) peer-reviewed studies supporting the treatment for your diagnosis, (3) CMS National Coverage Determinations showing Medicare covers the service, (4) documentation of conservative treatments that failed, and (5) clinical guidelines from professional medical societies. AppealArmor automatically finds and cites the relevant CMS determinations and legal authorities for your specific situation.
Rates vary widely by insurer, state, and denial category. According to KFF, fewer than 1 in 500 denied claims are ever appealed — and when patients do appeal, a meaningful share are overturned on internal review. External independent reviews, tracked by HHS OIG and state insurance departments, overturn denials at rates that often exceed 40%. The key variable is documentation quality: appeals backed by treating-physician letters, peer-reviewed evidence, and CMS coverage determinations consistently outperform bare appeals. Do not give up without filing.
The ACA (42 USC 300gg-19) guarantees appeal rights for all marketplace and individual plans. ERISA Section 503 governs employer-sponsored plans and requires full and fair review. State insurance laws add protections including independent medical review, timely response requirements, and the right to file complaints with your state insurance commissioner. AppealArmor identifies which laws apply to your specific plan type and state.
Absolutely, and your doctor's participation dramatically increases your chances. Ask your physician for a "letter of medical necessity" that explains the clinical rationale, references peer-reviewed studies, documents your treatment history, and describes the consequences of not receiving the treatment. Courts consistently give weight to the treating physician's judgment over the insurer's desk reviewer.
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