Medical Necessity Appeals: Countering with Clinical Evidence

"Not medically necessary" is the most frequently cited reason for health insurance denials — and one of the most frequently overturned on appeal. The key to winning is understanding exactly how insurers define medical necessity, what evidence they require, and how to present a compelling clinical argument. This guide walks you through the complete strategy.

How Insurers Define "Medical Necessity"

Despite being a central concept in health insurance, "medical necessity" has no single universal definition. Most health plans define it as care that is: (1) appropriate for the diagnosis or condition; (2) provided in accordance with generally accepted standards of medical practice; (3) not primarily for the convenience of the patient or physician; and (4) the most cost-effective service that can safely and adequately address the medical need.

Critically, insurers typically use proprietary clinical review tools — primarily Milliman Care Guidelines (MCG) and InterQual — to make these determinations. These are evidence-based criteria sets, but they are not the only measure of medical necessity. Courts have repeatedly held that insurers cannot mechanically apply these criteria without considering the individual patient's clinical circumstances.

Why Medical Necessity Denials Are Winnable

Medical necessity denials are overturned at a significant rate because:

• The insurer's reviewer may lack specialty expertise relevant to your condition
• Proprietary criteria like MCG/InterQual often lag behind current clinical practice
• Your treating physician has direct clinical knowledge the reviewer lacks
• The denial may fail to account for your specific clinical circumstances
• The criteria used may not match your plan's actual plan documents
• Procedural defects in the denial give you additional grounds to challenge

Step 1: Get the Specific Criteria Used

Before writing your appeal, request the specific criteria. Under 29 CFR §2560.503-1(g)(1)(viii) and 45 CFR §147.136(b)(2), the insurer must provide:

• The specific clinical criteria or guidelines relied upon
• Whether those criteria were MCG, InterQual, or proprietary plan criteria
• The specific section(s) of the criteria that were applied
• The qualifications of the reviewing clinician

Once you have these, your physician can respond specifically to each criterion, explaining point-by-point why the patient's presentation does or does not meet each element, and why the criteria are insufficient or inapplicable for this patient's unique circumstances.

Step 2: Build Your Clinical Evidence Package

A successful medical necessity appeal typically includes several layers of evidence:

Layer 1: Treating Physician's Letter of Medical Necessity

This is the cornerstone of your appeal. An effective LMN is not a one-paragraph generic letter. It should be a detailed clinical document that includes: the diagnosis with ICD-10 code(s); the clinical history and symptom progression; all prior treatments tried with doses, durations, and outcomes; why those alternatives were insufficient; the clinical basis for recommending the requested treatment; and the consequences of continued denial. Use our LMN Generator to create a professional template.

Layer 2: Peer-Reviewed Clinical Literature

Pull 2-3 key peer-reviewed studies or meta-analyses that support your treatment for your specific indication. PubMed (pubmed.ncbi.nlm.nih.gov) is free and searchable. Look for systematic reviews and randomized controlled trials. The more directly the study population matches your situation, the stronger the argument.

Layer 3: Clinical Practice Guidelines

Major medical societies publish treatment guidelines that carry significant weight in appeals. Relevant guidelines sources include:

• NCCN (National Comprehensive Cancer Network) — oncology guidelines
• AHA/ACC — cardiology guidelines
• ACR — rheumatology and radiology guidelines
• APA — psychiatry and mental health guidelines
• USPSTF — preventive care recommendations
• UpToDate — while behind a paywall, physicians can print relevant sections

Step 3: Challenge the Reviewer's Qualifications

Under ERISA §503 and ACA regulations, the clinician reviewing your case must have appropriate expertise. A general internist reviewing a specialized oncology treatment, for example, may not be qualified to make the determination. Request the reviewer's credentials as part of your appeal.

If the reviewer lacked appropriate specialty training, this is grounds to demand a new review by a physician with the relevant specialty expertise.

Step 4: Cite the Correct Legal Standard

When writing your appeal, cite these key legal standards:

• The Wit v. United Behavioral Health ruling (N.D. Cal. 2019): Established that insurers cannot use internally developed criteria that deviate from generally accepted standards of care. While applicable primarily to behavioral health, the principle extends more broadly.
• 29 CFR §2560.503-1(b)(7): Prohibits plan documents from "failing or refusing to comply" with the full and fair review requirements.
• ACA §2719: Requires non-grandfathered plans to have a meaningful internal appeals process that considers all information submitted by the claimant.

Sample Winning Argument Structure

1. State the denial: "On [date], [insurer] denied coverage for [treatment] citing 'not medically necessary.'"
2. Challenge the criteria: "The denial relies on [criteria], which does not adequately reflect [patient's specific situation] because..."
3. Present clinical evidence: "The treating physician, [name], has documented [specific clinical findings]. Published guidelines from [organization] indicate..."
4. Cite consequences: "Continued denial of this treatment will result in [specific health consequences]."
5. Request reversal: "For these reasons, we request immediate reversal and approval of [treatment]."