Medical Claim Review 101: Process, Denials, and How to Appeal Successfully

Table of Contents#

1. What Is Medical Claim Review, and Why Does It Matter?
2. Step-by-Step Medical Claim Review Process
3. Most Common Reasons for Medical Claim Denials
4. How to Appeal a Denied Medical Claim: 5 Actionable Steps
5. Pro Tips to Avoid Claim Denials Upfront
6. References

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What Is Medical Claim Review, and Why Does It Matter?#

Medical claim review is the standardized process insurance carriers use to verify that a submitted medical claim is valid, eligible for coverage, and accurately billed. Reviews are conducted for all claims, from routine doctor's visits to complex surgical procedures, and involve checks for billing errors, fraud, and alignment with your plan's coverage rules.

According to KFF's 2024 analysis of CMS transparency data, insurers on the federal Marketplace denied an average of 19% of in-network claims and 37% of out-of-network claims. Industry-wide, initial claim denial rates reached 11.8% in 2024, and each denied claim costs an average of $25 to$181 to rework. Understanding how the review process works can help you avoid or successfully challenge these denials.

This process benefits all parties:

• Patients: Avoid overpaying for services, catch incorrect denials, and ensure your plan covers eligible costs
• Providers: Receive accurate, timely reimbursement for services delivered
• Insurers: Prevent fraudulent billing and keep overall plan costs low for all members

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Step-by-Step Medical Claim Review Process#

Most claims are processed within 7-30 days, following this standard workflow:

Step 1: Claim Submission#

After you receive care, your provider (or you, if you paid out of pocket and are filing for reimbursement) submits a claim to your insurer. Claims include standard codes:

• ICD-10 codes for your diagnosis
• CPT/HCPCS codes for the services/procedures you received
• Your policy number, date of service, and provider's National Provider Identifier (NPI)

Step 2: Initial Administrative Review#

An automated insurer system first screens the claim for basic errors. Claims with no errors (called "clean claims") move to the next step. Claims with missing or incorrect information may be automatically denied or sent back to the provider for correction. According to KFF's 2024 data, 25% of in-network claim denials were due to administrative reasons (such as duplicate claims, missing information, or untimely filing), making this a major source of preventable denials.

Step 3: Medical Necessity Review#

For non-routine, high-cost, or elective services, the insurer's clinical team (registered nurses, board-certified physicians) reviews the claim to confirm:

• The service is medically necessary to treat your diagnosed condition
• The service is not considered experimental, cosmetic, or excluded from your plan
• The level of care matches your medical needs (e.g., no unnecessary inpatient admissions)

Step 4: Adjudication#

The insurer applies your plan terms to calculate payment amounts:

• Applies in-network vs. out-of-network pricing rules
• Deducts your remaining annual deductible, copay, and coinsurance amounts
• Calculates the total amount the insurer will pay the provider, and the total you owe

Step 5: Notification#

You and your provider receive an EOB that states if the claim is fully approved, partially approved, or denied, with a line-item breakdown of all costs and the reason for any denial.

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Most Common Reasons for Medical Claim Denials#

Denials fall into three core categories, each with different resolution paths:

1. Administrative Denials (Easiest to Resolve)#

• Missing or incorrect patient/policy information
• Claim filed after the plan's submission deadline (usually 90-180 days post-service)
• Prior authorization was not obtained for a service that requires it
• Incorrect coding (e.g., a procedure code that does not match your diagnosis)
• Duplicate claim submitted for the same service
• Service was provided by an out-of-network provider without pre-approval

2. Medical Necessity Denials#

• The insurer deems the service not required to treat your condition
• The service is classified as experimental/investigational
• The service is cosmetic (unless required for reconstructive care after an injury or illness)

3. Coverage Limitation Denials#

• The service is explicitly excluded from your plan (e.g., fertility treatments, weight loss surgery for many plans)
• You have hit your annual or lifetime benefit cap for the service type
• Your insurance was not active on the date of service

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How to Appeal a Denied Medical Claim: 5 Actionable Steps#

Per the Affordable Care Act, all insured Americans have the right to appeal denied claims. Follow these steps for the highest chance of success:

Step 1: Review Your Denial Letter and Plan Documents First#

Your denial letter is required by law to list the exact reason for the denial, the relevant plan clause, and your appeal deadlines (usually 180 days from the EOB date). Cross-check the denial with your official plan document to confirm the insurer applied your coverage rules correctly.

Step 2: Gather Supporting Documentation#

Work with your treating provider to collect evidence to support your appeal:

• A formal letter of medical necessity from your provider explaining why the service was required
• Relevant medical records, test results, and treatment plans
• Written proof of prior authorization if you obtained it
• Peer-reviewed clinical studies if the service was denied as experimental
• Receipts if you already paid for the service out of pocket

Step 3: File a First-Level Internal Appeal#

Submit your appeal packet to your insurer's appeals department via certified mail (with return receipt) or their secure online portal for tracking. Include a cover letter clearly stating why you disagree with the denial. A sample opening is below:

Sample Appeal Letter Opening Date: [Insert Date] Your Name: [Full Name] Policy Number: [XXX-XXX-XXX] Claim Number: [XXX-XXX-XXX] To [Insurer Appeals Department], I am writing to appeal the [Date of EOB] denial of my claim for [name of service] received on [date of service] from [provider name]. The claim was denied for [reason listed on denial letter], but the attached documentation confirms the service is medically necessary and covered under my plan. I request you review this evidence and overturn the denial.

Insurers are required to respond to internal appeals within 30 days for pre-service claims, and 60 days for post-service claims. For urgent care situations, the decision must be made within 72 hours.

Step 4: Request an Independent External Review#

If your internal appeal is denied, you can request a review from an independent third-party organization not affiliated with your insurer, a right guaranteed by the ACA for most plans. The external reviewer's decision is binding on the insurer (you are not required to accept it if you wish to pursue further action). You have four months from the date of the internal appeal denial to submit this request. Standard external reviews must be completed within 45 days; expedited reviews for urgent situations must be decided within 72 hours. If your plan uses the HHS-administered Federal External Review Process, there is no charge. State processes may charge up to $25.

Step 5: Escalate if Needed#

If the external review rules against you, you can file a complaint with your state's Department of Insurance, contact your state's Consumer Assistance Program (if available), or work with a licensed patient advocate or medical billing attorney to explore further legal options.

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Pro Tips to Avoid Claim Denials Upfront#

1. Verify coverage before non-emergency care: Call your insurer to confirm the service is covered, and ask if prior authorization is required. Get all confirmations in writing.
2. Use in-network providers whenever possible: Out-of-network claims are denied at significantly higher rates (37% vs. 19% for in-network claims on ACA Marketplace plans in 2024, per KFF).
3. Keep detailed records: Save all EOBs, prior authorization confirmations, appointment notes, and provider bills in a dedicated folder.
4. Ask your provider to share a copy of the submitted claim: Review it for incorrect dates, codes, or patient information before it is sent to the insurer.
5. Work with your provider's billing team early: They have experience appealing denials and can often submit corrected claims on your behalf for faster resolution.
6. Know your appeal rights and deadlines: Fewer than 1% of denied claims are appealed, yet insurers overturn a significant share of appeals when properly documented. Mark your appeal deadlines on a calendar—missing a deadline can permanently forfeit your right to challenge a denial.

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References#

1. Kaiser Family Foundation. (2023). Consumer Survey Highlights Problems with Denied Health Insurance Claims. Retrieved from https://www.kff.org/affordable-care-act/consumer-survey-highlights-problems-with-denied-health-insurance-claims/
2. Kaiser Family Foundation. (2026). Claims Denials and Appeals in ACA Marketplace Plans in 2024. Retrieved from https://www.kff.org/patient-consumer-protections/claims-denials-and-appeals-in-aca-marketplace-plans-in-2024/
3. Commonwealth Fund. (2026). How Health Insurance Coverage Denials Affect Americans: Findings from the 2025 Affordability Survey. Retrieved from https://www.commonwealthfund.org/publications/surveys/2026/jun/how-health-insurance-coverage-denials-affect-americans-2025-affordability-survey
4. Centers for Medicare & Medicaid Services. (2025). Internal Claims and Appeals and the External Review Process Overview. Retrieved from https://www.cms.gov/marketplace/technical-assistance-resources/internal-claims-and-appeals.pdf
5. HealthCare.gov. External Review. Retrieved from https://www.healthcare.gov/appeal-insurance-company-decision/external-review/