As an employer or HR leader selecting a health plan, understanding how insurers determine "medical necessity" is key. This standard directly impacts your employees' access to care, their out-of-pocket costs, and your company's healthcare spend and workforce well-being. A medically necessary service is one needed to diagnose or treat an illness, injury, condition, disease, or its symptoms, and that meets accepted standards of medicine. Applying that definition is more complex than it sounds. It involves clinical guidelines, policy language, and regulatory frameworks.
The Foundational Criteria for Medical Necessity
Insurers don't make these decisions on a whim. They use a structured framework. Criteria vary by carrier and plan, but these pillars are almost universal:
- Accepted Standards of Care: Is the treatment consistent with the symptoms or diagnosis? Is it not primarily for convenience?
- Clinically Appropriate: Is it provided for diagnosis, direct care, and treatment of the condition? Does it follow nationally recognized, evidence-based guidelines (e.g., from medical specialty societies)?
- Not Experimental or Investigational: Is the treatment established and effective based on peer-reviewed studies, not part of a clinical trial?
- Site-of-Service Appropriateness: Can care be safely and effectively provided in a less intensive setting (e.g., outpatient vs. inpatient)?
The Step-by-Step Determination Process
When a provider submits a request, it goes through a structured review. A typical request moves through four steps:
- Initial Automated Review: Many routine requests are checked against the plan's clinical policies and edits (like age limits or frequency rules) via automated systems. If it passes, approval is instant.
- Clinical Review by Medical Staff: If the request is flagged (due to complexity, cost, or deviation from guidelines), it's reviewed by the insurer's in-house nurses and doctors. They compare the patient's clinical info against insurers' evidence-based guidelines.
- Peer-to-Peer Review: If the initial review suggests a denial, the treating physician can often speak directly with the insurer's reviewing physician to provide context or advocate for the treatment.
- Independent External Review: If an internal appeal still results in a denial, the ACA grants members of non-grandfathered plans the right to an independent review by an outside organization. That reviewer's decision is binding on the insurer, though the member can still pursue other legal remedies.
The appeal path is also underused. KFF's analysis of federal data found HealthCare.gov insurers denied roughly 85 million in-network claims in 2024, and consumers appealed fewer than 1% of them. Insurers upheld 66% of internal appeals. External review tells a different story. KFF found outside reviewers overturned almost half of the initial denials they examined.
State and Federal Limits on Automated Denials
Automated review is now bounded by new rules. In a February 2024 FAQ, CMS told Medicare Advantage plans that algorithms and AI may assist coverage decisions but may not override medical necessity standards, and that a denial must reflect the individual patient's circumstances rather than a larger dataset. California went further. Its Physicians Make Decisions Act (SB 1120), effective January 1, 2025, bars health plans from denying, delaying, or modifying care based solely on an AI algorithm and requires the final medical necessity determination to come from a licensed physician or qualified clinician with relevant expertise. The law also requires plans to disclose their use of AI in utilization review and to audit those tools. Other states have followed, including Illinois, which limits adverse determinations to a clinical peer and forbids relying solely on an algorithmic process, and Texas, which bars AI as the sole basis for an adverse decision. For employers, the practical questions are who governs the automated review, who signs off on a denial, and what disclosure and audit obligations the plan follows.
Key Tools and Guidelines Used by Insurers
The "accepted standards" insurers refer to are codified in specific resources. Knowing these demystifies many coverage decisions.
- Evidence-Based Clinical Policy Bulletins (CPBs): These are the insurer's proprietary guidelines detailing coverage positions on thousands of procedures, devices, and drugs.
- MCG or InterQual Criteria: Widely used, commercially available clinical criteria. MCG, formerly Milliman Care Guidelines, is part of Hearst Health, and InterQual is owned by Optum. Both help determine the appropriateness and length of hospital stays and the need for certain procedures.
- FDA Approval and Drug Formularies: For medications, FDA approval is a baseline. Insurers then use Pharmacy & Therapeutics (P&T) committees to place drugs on formulary tiers based on efficacy, safety, and cost.
- Plan Document Exclusions: The employer's specific plan document is king. Even a medically necessary service can be denied if it's explicitly excluded (e.g., cosmetic surgery, certain fertility treatments).
The Employer's Role and Strategic Considerations
You're not powerless in this process. Your choice of carrier, plan design, and advocacy support directly shapes outcomes. Work with brokers who know insurers' clinical policies. Consider adding a patient advocacy or nurse concierge service, like the one in the WellthCare ecosystem, to guide employees through prior authorizations and appeals. That helps employees secure necessary care while minimizing wasteful claims. WellthCare, the first Health-to-Wealth Benefit System, approaches the same goal from the prevention side, rewarding every verified preventive action with spendable store dollars and automatic retirement contributions, compounding health and wealth. It's a system that fights for employees' health while protecting the plan's financial integrity.
Medical necessity decisions are clinical, but they're tied to your benefits strategy. Choose partners and plans that favor transparent, evidence-based medicine and strong member advocacy. That builds a system where employees get the care they need and a healthier, more productive workforce.