What Evidence Do You Need to Win an Insurance Appeal?

Your appeal is only as strong as your evidence. A perfect letter without documentation loses to a weak letter with strong evidence.

This guide shows you exactly what evidence wins appeals, how to organize it, and what to emphasize to different reviewers.

The Evidence Hierarchy

Not all evidence is equal. Here's the power ranking:

Tier 1: Your Treating Doctor's Letter

This is the most powerful piece of evidence.

Why: Your doctor examined you, knows your complete medical history, and understands your specific situation. Their professional opinion carries enormous weight.

What it should say:

• Clear diagnosis
• Medical history relevant to the claim
• Why the treatment is medically necessary
• Clinical reasoning (not just "I think it's good")
• How long this is standard of care
• What happens without the treatment
• Refutation of the insurer's specific objection

Format: Letter on official letterhead, signed by the doctor.

Example: "[Patient name] has been diagnosed with [condition]. This condition is characterized by [specific findings]. The recommended treatment is [treatment], which is the standard of care for this condition in my specialty. The treatment is medically necessary in this case because [specific reasons]. Without this treatment, [patient name] faces [specific risks]. The [insurer] denial appears to be based on [insurer's reason], but this does not align with clinical evidence. I strongly support approval of this claim."

Tier 2: Clinical Guidelines

Clinical guidelines show that your treatment is standard of care. They're respected, objective, and influential.

What counts:

• NCCN (National Comprehensive Cancer Network)
• ASCO (American Society of Clinical Oncology)
• Specialty society guidelines
• Government health authority guidelines
• International guidelines (if local aren't available)

How to use:

• Print the relevant passage
• Highlight the specific recommendation
• Cite in your appeal letter by name and version
• Attach as evidence

Example: "According to the NCCN Clinical Practice Guidelines for [condition] (version 2025), [treatment] is recommended for patients with [diagnosis]. This supports the medical necessity of my claim."

Tier 3: Medical Records

Complete medical records often reverse denials. Incomplete ones often cause them.

What to include:

• Diagnosis documentation with dates
• All test results and imaging
• Hospital or clinic records
• Any specialist consultations
• Treatment history
• Prior authorizations or approvals for similar treatments

Why it matters: Complete records show the full clinical picture. The insurer's reviewer might not have received everything the first time.

Tier 4: Published Research

Clinical trials and peer-reviewed studies supporting your treatment add credibility.

Where to find:

• PubMed (pubmed.ncbi.nlm.nih.gov)
• Google Scholar (scholar.google.com)
• Specialty society publications
• Major medical journals

How to use: Print key studies, highlight relevant passages, cite in your appeal.

Tier 5: Comparative Cases

If your insurer has approved the same treatment for other patients, that's powerful.

How to find: Ask your doctor, patient advocacy groups, or search your insurer's decisions.

How to use: "The insurer has previously approved [treatment] for patients with [similar diagnosis]. My case is comparable. The prior approval demonstrates the treatment is recognized by the insurer as medically necessary."

Evidence by Denial Reason

Different denials require different evidence focus.

For "Not Medically Necessary" Denials

Priority 1: Doctor's letter explaining clinical necessity Priority 2: Clinical guidelines supporting treatment Priority 3: Medical records showing condition severity Priority 4: Published research showing treatment effectiveness Bonus: Peer-to-peer review request

For "Pre-Existing Condition" Denials

Priority 1: Medical records with diagnosis/symptom dates Priority 2: Doctor's letter confirming condition timing Priority 3: Original policy application (showing what you disclosed) Priority 4: Communications with the insurer about the condition Bonus: Regulatory guidance on pre-existing condition limits

For "Prior Authorization Denied"

Priority 1: Doctor's letter explaining urgency or medical necessity Priority 2: Medical records showing condition severity Priority 3: Clinical guidelines supporting authorization Priority 4: Evidence of prior authorization approvals for similar cases Bonus: Request for peer-to-peer review

For "Out-of-Network Denial"

Priority 1: Evidence of emergency (ER records, hospital admission) OR evidence of prior in-network relationship OR evidence of no adequate in-network options Priority 2: Doctor's letter explaining why this specific provider is necessary Priority 3: Insurer's provider directory showing network gaps Priority 4: Facility records proving the facility was in-network

For "Exclusion Applies"

Priority 1: Policy language that contradicts the exclusion Priority 2: Doctor's letter explaining treatment for a covered condition Priority 3: Clinical guidelines showing treatment is standard Priority 4: Evidence of industry standards contradicting the exclusion

Organizing Your Evidence

Organization matters. Reviewers spend 10-15 minutes on your case. Make it easy for them to find what they need.

Create an Evidence Index

List everything you're submitting:

"Attached Evidence:

1. Attachment A: Dr. [name]'s letter dated [date] explaining medical necessity
2. Attachment B: NCCN Guidelines passages supporting [treatment]
3. Attachment C: Complete medical records from [dates]
4. Attachment D: Hospital discharge summary dated [date]
5. Attachment E: My policy language addressing [specific issue]"

Then label each attachment: "Attachment A - Doctor's Letter"

Use a Folder or Binder

If submitting by mail, use a folder or 3-ring binder with labeled tabs:

• Tab 1: Denial Letter (original)
• Tab 2: Your Appeal Letter
• Tab 3: Doctor's Letter
• Tab 4: Clinical Guidelines
• Tab 5: Medical Records
• Tab 6: Policy Language
• Tab 7: Other Evidence

Use Strategic Highlighting

Highlight key points in evidence documents:

• In doctor's letter: highlight the clear recommendation
• In guidelines: highlight the specific recommendation
• In medical records: highlight diagnostic findings
• In policy: highlight language supporting your case

Don't highlight everything. Highlight only the key points (1-2 per page maximum).

Include a Cover Sheet

Create a simple cover sheet:

"INSURANCE APPEAL PACKAGE

Claimant: [Your name] Policy Number: [number] Claim Number: [number] Appeal Date: [date] Claim Denial Date: [date] Treatment/Service: [description]

This package contains: [number] documents with evidence supporting the appeal for [treatment]. Key evidence includes [brief summary]."

This helps the reviewer understand what they're looking at.

Evidence Presentation Tips

1. Original + Copy

Provide originals when possible (doctor's letter), copies for other documents.

2. Legibility

Scans should be clear and readable. Don't submit blurry faxes or bad photos.

3. Dates and Labels

Every document should have:

• Date (when created or when you're submitting)
• Source (who created it, which organization)
• Relevance (brief note explaining why it's included)

4. Medical Records Chronologically

Organize medical records by date, oldest to newest. This tells the story of your condition's development.

5. Remove Irrelevant Pages

If submitting medical records, remove pages that aren't relevant (unrelated appointments, billing statements, etc.). Keep only clinically relevant records.

Red Flags: Evidence That Backfires

Don't Submit:

• Emotional letters from friends/family: These hurt, not help. The insurer needs medical facts, not sympathy.
• Social media posts about your illness: Can be used against you if they contradict your claim.
• Internet research about your condition: Leave medical interpretation to doctors.
• Complaints about the insurer's decision-making: Stick to facts, not accusations.
• Multiple copies of the same document: One copy is enough.
• Anything that makes your claim seem exaggerated: Stick to facts.

Don't Omit:

• Medical records showing prior similar treatments: Even if the insurer previously denied, showing a pattern helps your case.
• Records showing you've tried alternatives: If you failed first-line treatment, that proves your requested treatment is necessary.
• Dates and timelines: These are crucial for pre-existing condition disputes, authorization arguments, etc.

Special Evidence by Country

USA

• ACA plans: Include reference to ACA protections
• Employer plans: Include reference to ERISA
• Prior auth denials: Include evidence of emergency (ER records) if applicable

UK

• FOS appeals: Include reference to FCA conduct rules
• IPID disputes: Include the Insurance Product Information Document you received at sale
• Timeline issues: Reference the 8-week rule

Australia

• AFCA appeals: Include reference to Australian Consumer Law
• ACL unfairness: Show how exclusion/denial violates fair dealing standards

Singapore/Malaysia/Hong Kong

• Regulator references: Include MAS, BNM, or IA guidance on claims handling
• Timeline evidence: Show when you notified the insurer

Getting Medical Evidence

From Your Doctor

Email or call your doctor's office: "I need a detailed letter on letterhead describing my condition and why [treatment] is medically necessary. This is for my insurance appeal. Can you provide this by [date]?"

Most doctors are happy to help. Offer to provide a draft they can refine.

Getting Your Medical Records

Contact the hospital or clinic where you were treated: "I need copies of all medical records for [date range]. I'll pay any reasonable fee."

They usually respond within 5-10 business days.

Finding Clinical Guidelines

• Search [guideline name] + PDF
• Visit specialty society websites
• Check the treatment's Wikipedia page (often links to guidelines)
• Ask your doctor for copies

Getting Published Research

• PubMed.gov (free)
• Google Scholar (free)
• ResearchGate.net (researchers often share papers)
• Ask your doctor for copies of key studies

Evidence You Might Not Think Of

Prior Approvals

If your insurer previously approved this treatment (for you or other patients), that's powerful evidence.

Ask the insurer: "Have you previously approved [treatment] for other patients with [diagnosis]?"

If yes, cite that: "The insurer has recognized this treatment as medically necessary in prior cases. My case is comparable."

Industry Standards

If your doctor says "this is standard treatment in my field," get them to document it.

Ask: "Is this treatment standard of care in your specialty?"

Get their confirmation in writing.

Cost-Effectiveness

Some treatments are expensive. If you can show the treatment is cost-effective (prevents more expensive interventions), that helps.

Example: "This preventive treatment costs $X. Without it, the condition progresses, requiring $Y hospitalization. The treatment is cost-effective."

Evidence Checklist

Before submitting your appeal, verify you have:

• Doctor's letter on official letterhead, signed
• Clinical guideline passages (printed, highlighted)
• Complete medical records with dates
• Hospital/specialist records (if applicable)
• Published research supporting treatment (if available)
• Policy language supporting your position
• Any communications from the insurer about coverage
• Timeline evidence (dates of notification, denial, etc.)
• Evidence of prior similar approvals (if applicable)
• Everything organized with cover sheet and index

The stronger your evidence pack, the faster your approval.

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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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