Insurance Claim Denied as 'Not Medically Necessary': How to Fight Back

"Not medically necessary." It's one of the most common reasons insurers deny claims. It's also one of the most frequently overturned on appeal.

This guide shows you exactly how to challenge a not medically necessary insurance denial. You'll learn what the term means, why insurers use it, and how to build an argument that reverses the decision.

The key: insurers use vague "medical necessity" language because it gives them flexibility. But that flexibility also makes it vulnerable to challenge. With the right evidence, most NMN denials fail.

What Does "Not Medically Necessary" Actually Mean?

This is where many people get confused. Insurance companies don't define "medically necessary" the same way your doctor does.

Your Doctor's Definition: The treatment will help your condition. It's reasonable. It aligns with how medical professionals typically treat your problem.

The Insurer's Definition: The treatment meets the insurer's clinical criteria AND is appropriate for your specific diagnosis AND doesn't exceed what the insurer's guidelines allow.

This is the gap. Your doctor thinks it's necessary. The insurer's medical reviewer thinks it costs too much or isn't "proven enough" by the insurer's standards.

Understanding this gap is how you win.

How Insurers Define "Medical Necessity"

Most insurers use one of three frameworks:

1. Milliman Guidelines Milliman publishes clinical treatment guidelines that many insurers use. They're evidence-based, but they're conservative—they often don't approve newer treatments even if doctors use them.

If your insurer denied you based on Milliman, you can challenge by:

• Showing your doctor's clinical opinion (which may be more progressive)
• Providing clinical guidelines from other respected sources (NCCN, ASCO, specialty societies)
• Showing that current medical practice has evolved beyond Milliman's standards
• Proving the treatment is standard of care in your region

2. InterQual Criteria InterQual creates clinical decision-making tools. Again, they're evidence-based but often conservative.

Challenge InterQual denials with:

• Your treating doctor's letter explaining why the treatment is necessary for your specific case
• Clinical guidelines that support the treatment
• Evidence of how it's practiced in your community
• Recent research showing the treatment's effectiveness

3. The Insurer's Own Criteria Some insurers create custom criteria. These are often the easiest to challenge because:

• They may not align with standard medical practice
• They're sometimes outdated
• They may not account for your individual circumstances

Challenge custom criteria with:

• Your doctor's detailed clinical reasoning
• National/international guidelines
• Evidence of standard practice
• Proof that similar patients receive the same treatment

Why Insurers Use "Not Medically Necessary" as a Denial

Be clear-eyed about this: insurers use NMN denials because they save money.

If the insurer approves your claim, they pay. If they deny it, they don't. They have financial incentive to deny.

The insurer's medical reviewer (often a doctor hired by the insurance company) evaluates your case. But that doctor works for the insurer. There's built-in bias toward denying expensive treatments.

This doesn't mean the insurer is acting in bad faith—but it means they're not neutral. Your treating doctor is neutral on cost. The insurer's reviewer isn't.

This is why appeals work: an independent reviewer (at AFCA, FOS, OLHI, etc.) will often overturn the insurer's decision because they can see the bias.

Why NMN Denials Are Often Wrong

Here's the secret: most NMN denials fail because the insurer's reasoning doesn't hold up.

Common reasons they're wrong:

1. The insurer ignored your treating doctor Your doctor knows your case intimately. They examined you, reviewed your history, and understand your specific circumstances. The insurer's medical reviewer read a file.

Your doctor's opinion should carry weight. If the insurer dismissed it without explanation, that's a weakness.

2. The insurer relied on outdated guidelines Medical practice evolves. A treatment that wasn't standard 5 years ago might be standard now. If the insurer's guidelines are old, that's a vulnerability.

Cite current guidelines in your appeal.

3. The insurer didn't consider your individual circumstances Medical necessity isn't one-size-fits-all. Your specific situation might require treatment that would be unnecessary for most patients.

If the insurer made a blanket decision without considering your individual factors, that's wrong.

4. The insurer confused "experimental" with "not medically necessary" Experimental treatments are unproven. Medically necessary treatments are proven to work but the insurer thinks they're not needed in your case.

If the treatment is established and recommended by specialists, it's not experimental—it's just maybe not their preferred first choice.

5. The insurer used a lower standard of evidence than medical practice requires Insurers sometimes demand more evidence than doctors do. They want "proven beyond doubt" when "established and recommended by specialists" is actually the medical standard.

Challenge this with: clinical guidelines that support the treatment at a lower evidence threshold than the insurer used.

Building Your Medical Necessity Argument

Here's how to build an argument that wins:

Step 1: Get Your Doctor's Written Support

This is crucial. You need a letter from your treating doctor that addresses the insurer's specific objection.

What the letter should include:

• Clear statement: "In my professional medical opinion, [treatment] is medically necessary for [your diagnosis]"
• Explanation of your condition, severity, and prognosis
• Why this specific treatment is appropriate for your situation
• How long it's been standard practice in your field
• What would happen if you don't receive the treatment (prognosis without treatment)
• References to clinical guidelines supporting the treatment
• Explanation of why you're an appropriate candidate (if relevant)

What NOT to include:

• Emotional language
• Criticism of the insurer
• Claims about what's "obviously" necessary (doctors know NMN denials are opinion-based)

Example structure: "[Patient name] has been diagnosed with [condition]. This condition is characterized by [specific symptoms/test results]. The recommended treatment by the [specialty] field is [treatment]. In [patient name]'s case, this is particularly necessary because [specific factors]. The [treatment] has been standard of care for [number] years and is supported by [guideline reference]. Without this treatment, [patient name] faces [specific risk]. I strongly recommend approval."

Step 2: Research Clinical Guidelines

Clinical guidelines are your evidence. They show what doctors actually do.

Key guidelines by specialty:

• Oncology: NCCN (National Comprehensive Cancer Network), ASCO (American Society of Clinical Oncology)
• Cardiology: ACC (American College of Cardiology), AHA (American Heart Association)
• Mental Health: APA (American Psychiatric Association), NICE (UK)
• Rheumatology: ACR (American College of Rheumatology)
• Specialist societies: Most medical specialties have professional organizations with treatment guidelines

In your appeal, cite these guidelines directly. Quote the relevant passage. Show that your treatment aligns with current, respected guidelines.

Example: "According to the National Comprehensive Cancer Network guidelines (version 2025), treatment with [drug] is recommended for patients with [your diagnosis]. The insurer's denial contradicts this established guideline."

Step 3: Find Evidence of Standard Practice

Show that the treatment is actually used by doctors in your region.

How:

• Ask your doctor: "Is this treatment standard of care for my condition in this area?"
• Research specialty society recommendations
• Look for published studies showing the treatment's use
• Find comparable case approvals (if your insurer has approved similar claims)

In your appeal: "This treatment is standard of care in [specialty] for [diagnosis]. It's recommended by [guideline]. Doctors across [country/region] routinely prescribe this for my condition."

Step 4: Address the Insurer's Specific Objection

If the insurer said the treatment is "experimental," explain why it's not.

If the insurer said it's "not proven," cite evidence.

If the insurer said it "exceeds standard of care," show that it doesn't.

Go direct to what the insurer said and rebut it point by point.

The Power of the Peer-to-Peer Review

Here's a tactic that often works immediately: request a peer-to-peer review.

This means your doctor talks directly to the insurer's medical reviewer. Doctor to doctor. In real time.

Why it works: Most NMN denials happen because the insurer's reviewer did a quick file review and made a conservative decision. When your doctor explains the clinical reasoning directly, the decision often flips immediately.

In your appeal, write: "I request a peer-to-peer review between my treating physician [name] and the insurer's medical director. My physician is available [dates/times]. This conversation should address the clinical basis for the denial."

Provide your doctor's contact information. Encourage them to take the call. Many insurers will immediately reverse the denial after this conversation.

Common Medical Necessity Denial Patterns

Pattern 1: "First-line treatment not exhausted" The insurer says you haven't tried the cheaper option yet. Challenge with: your doctor's explanation of why the first-line won't work for you, side effects you've experienced, medical reason the first-line isn't appropriate.

Pattern 2: "Treatment is off-label" The insurer says the treatment isn't FDA-approved for your specific diagnosis. Counter: many standard treatments are used off-label; your doctor's clinical judgment supports it; guidelines support off-label use.

Pattern 3: "Insufficient evidence" The insurer says there aren't enough studies. Show: the treatment has established clinical use; it's recommended in guidelines; doctors routinely prescribe it.

Pattern 4: "Treatment is new/experimental" Counter: the treatment has been used for [number] years; it's in standard guidelines; clinical trials show effectiveness.

Pattern 5: "Your condition isn't severe enough" Challenge with: your doctor's assessment of severity; test results showing disease progression; risk without treatment.

Evidence Pack for NMN Appeal

Organize your evidence clearly:

1. Doctor's Letter (most important)

• Your treating doctor's detailed medical necessity letter
• Any specialist letters supporting the treatment

2. Clinical Guidelines

• Printed copies of relevant guideline passages supporting the treatment
• Highlighted sections showing the treatment's recommendation
• Date of guidelines (to show they're current)

3. Medical Records

• Your diagnosis documentation
• Test results showing condition severity
• Treatment history (including failed prior treatments, if relevant)

4. Research/Evidence

• Copies of published studies on the treatment (if available)
• Comparison to similar approved cases (if you can find them)
• Specialty society recommendations

5. The Insurer's Denial

• Highlighted sections showing the specific NMN reasoning
• Your rebuttal of each point

Writing Your NMN Appeal Letter

Structure it clearly:

Paragraph 1: "The insurer denied my claim based on [specific NMN reason]. I am appealing this decision."

Paragraph 2: "The denial is inconsistent with my treating physician's medical judgment. [Dr. name] states [key quote from doctor's letter]."

Paragraph 3: "The treatment is supported by established clinical guidelines. [Guideline name] recommends this treatment for [your diagnosis]. [Quote from guideline]."

Paragraph 4: "This treatment is standard of care in [specialty] for [condition]."

Paragraph 5: "My specific circumstances support medical necessity because [factors specific to you]."

Paragraph 6: "I respectfully request that the insurer reconsider and approve the treatment. I am available for a peer-to-peer review if the medical director wishes to discuss the clinical basis for approval."

Attachments: Doctor's letter, guideline passages, medical records, research.

ClaimBack can analyse your case and write your appeal letter in minutes — Start Free →

We'll analyze your specific denial, your medical records, clinical guidelines, and generate a professional medical necessity argument that addresses the insurer's specific objections.

Timeline Expectations

• Insurer review of appeal: 30 days
• If escalated to external review: 30-72 days
• Total: 1-3 months in most cases

Many insurers flip NMN denials within 30 days of receiving strong medical evidence and a peer-to-peer request.

When NMN Denials Are Actually Legitimate

Be honest: sometimes the insurer is right. If:

• Your condition isn't severe enough to require treatment yet
• The treatment isn't established or proven
• You haven't exhausted all prior options and there's good reason to try them first
• The treatment is truly experimental

...then the denial might be justified.

But these are rare. Most NMN denials fail because the insurer was too conservative, not because the insurer was correct.

Final Checklist

• I have my insurer's specific NMN objection in writing
• I have a detailed letter from my treating doctor supporting necessity
• I have researched and copied relevant clinical guidelines
• I have organized my medical records showing condition severity
• I have drafted a point-by-point rebuttal of the insurer's reasoning
• I have requested a peer-to-peer review
• I know my insurer's appeal deadline
• I have contact information for external review (AFCA, FOS, etc.) if needed

Medical necessity is subjective. That's your opportunity. Use it.

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Disclaimer: ClaimBack provides AI-generated appeal assistance for informational purposes only. ClaimBack is not a law firm and does not provide legal advice. Always review your appeal letter before sending and consider professional advice for complex or high-value claims. Regulatory processes vary — always verify current procedures with your insurer or regulator.

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