What does medically necessary mean for insurance?

"Medically necessary" means healthcare services or supplies needed to diagnose or treat an illness, injury, condition, disease, or its symptoms that meet accepted standards of medicine.

Insurers use this standard to decide which treatments, tests, or procedures they will pay for. If a service is not considered medically necessary, your insurance company will usually deny the claim.

Core Requirements for Medical Necessity

To qualify as medically necessary, a treatment must generally meet these rules:

• Meets clinical standards: It follows generally accepted standards of medical or clinical practice.
• Appropriate for the condition: It is right for your specific diagnosis in terms of type, frequency, extent, site, and duration.
• Serves a real medical purpose: It is used to evaluate, diagnose, or treat a condition rather than being done for convenience.
• Not cosmetic or experimental: It excludes purely cosmetic procedures, elective comforts, or unproven experimental treatments.
• Cost-effective: It is not significantly more expensive than an alternative service that would be just as effective.

How Insurance Companies Decide

Insurers evaluate treatments using medical records, clinical guidelines, and a review process:

• Prior Authorization: The insurer reviews and approves a treatment before you receive it to confirm it meets their rules.
• Letter of Medical Necessity: Your doctor may need to write a formal letter explaining why a specific treatment or piece of equipment is vital to your health.
• Claims Review: The insurer can look at your medical records after the service to verify that the care provided matched the diagnosis.

You can check official federal explanations on the HealthCare.gov Glossary or read the NAIC What Is Medical Necessity Guide for a deeper breakdown.

Getting a Letter of Medical Necessity (LMN) is usually not hard if the request is tied to a real, diagnosed medical condition.

How Hard Is It?

• Easy: If your regular doctor already treats you for a condition (like high blood pressure or chronic back pain) and you need an LMN for a directly related expense (like a specific exercise program or ergonomic chair). You can often request it through a patient portal message or a quick follow-up visit.
• Moderate: If your current doctor does not know you well, is unfamiliar with HSA/FSA paperwork, or if you use a dedicated digital health platform or a checkout service like Flex that includes a virtual consultation.
• Hard / Refused: If you ask a doctor to sign off on things that lack clinical backing, look like general lifestyle upgrades (like luxury hot tubs or non-qualifying emotional support animal requests), or use instant survey sites that do not perform a legitimate medical evaluation.

What Makes a Good Letter?

A valid letter from a licensed healthcare provider must include:

• Patient and provider info (name, license number, and credentials)
• Specific diagnosis with an official ICD-10 code
• Recommended treatment or product and how it treats the condition
• Duration (usually valid for a maximum of 12 months)
• Provider’s signature and date

A medical necessity denial happens when an insurance company decides a treatment, test, or service is not appropriate or needed for your specific condition.

Common Causes of Denials

• Insufficient Documentation: The medical notes do not clearly show the patient's symptoms, severity, or why the specific test or treatment was chosen.
• Mismatched Diagnosis and Procedure: The billing code for the treatment does not match the approved reasons listed in the insurer's coverage rules.
• Skipped Step Therapy: The provider did not try required cheaper or more conservative treatments first before moving to an advanced option.
• Wrong Treatment Setting: The care was given in an expensive setting, such as a hospital, when it could have been done safely in a cheaper setting, like an outpatient clinic or at home.
• Missing Prior Authorization: The doctor did not get approval from the insurance company before giving the service.
• Experimental Status: The insurance company views the treatment as unproven, investigational, or not standard medical practice for that diagnosis.
• Exceeded Limits: The patient used up the allowed number of visits or days in the hospital for that year.

You can learn more about managing these issues through the Healthcare Financial Management Association or review guidelines on Coronis Health regarding specific denial codes.

Yes, you can write a letter of medical necessity (LMN) for yourself if you are a licensed physician, but it is generally discouraged by tax and insurance experts due to a clear conflict of interest.

Key Considerations for Self-Authored LMNs

• Conflict of Interest: Writing your own letter for tax deductions (like an HSA/FSA reimbursement or medical expense deduction) creates a self-serving bias that insurance companies or the IRS may view as lacking credibility.
• Third-Party Verification: To pass an audit or insurance review, guidelines strongly recommend that a separate, independent healthcare provider who is actively treating you for the condition should evaluate and sign the document.
• Auditing Risk: If an HSA administrator or the IRS requests proof of medical necessity, a self-signed letter carries a high risk of rejection or denial because it lacks an objective, unbiased medical evaluation.

Insurance companies determine medical necessity by evaluating whether a treatment, test, or service aligns with their written clinical guidelines, standard medical practices, and the patient's specific health records.

Key Criteria Used

Insurers generally look for the following core elements when assessing a request:

• Clinical Appropriateness: The service must be effective and proper for diagnosing or treating an illness, injury, or disease.
• Accepted Standards: The treatment must match recognized, evidence-based standards of medical and clinical practice. It cannot be experimental or purely investigational.
• Not for Convenience: The care cannot be provided primarily for the convenience of the patient, family, or healthcare provider.
• Cost-Effectiveness: The service should not be significantly more expensive than an alternative treatment or setting that would be just as effective.
• Exclusion of Cosmetic Care: Procedures meant exclusively to enhance appearance rather than treat a physical or mental health impairment are excluded.

The Review Process

Insurers utilize formal review procedures to make these determinations, which can happen before, during, or after care:

• Prior Authorization: A pre-certification review conducted before a service is delivered to confirm it meets coverage rules.
• Concurrent Review: An evaluation performed while treatment is ongoing to decide if extended care or continued hospital stays remain necessary.
• Retrospective Review: A paper-based review of medical records and billing codes completed after services are rendered to verify compliance.
• Third-Party Criteria: Many health plans use standardized clinical guidelines provided by external organizations like Milliman or Interqual, alongside rules from the Centers for Medicare & Medicaid Services (CMS).