When a health plan says a treatment is “not medically necessary,” the denial can feel deeply personal. You and your doctor may view the care as essential, yet the plan may frame the dispute as a paperwork or criteria issue. That gap matters, because medical-necessity appeals often turn on how the case is documented, which plan rules were applied, and whether the denial notice actually explains the reason clearly enough to challenge it.
In this post you’ll learn seven common mistakes that often make these appeals harder, along with practical ways people often reframe the record before the next review. If you want a broader foundation first, it may help to start with our guide to how coverage fights over treatment approval usually work.
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A medical-necessity denial is rarely just a disagreement about medicine. In many cases, it is also a disagreement about the plan’s clinical criteria, the records submitted, the coding or service description, and the timing of the request.
That helps explain why appeals can be difficult even when the care seems plainly important. Federal consumer protections give many patients a right to internal appeal and, in many situations, independent external review when a plan denies care based on medical necessity, appropriateness, level of care, setting, or effectiveness of a covered benefit. Marketplace guidance also says internal appeals generally must be filed within 180 days of the denial notice, with faster timelines available for urgent cases. CMS, HealthCare.gov, and CMS’s external appeals overview all outline those protections.
At the same time, appeals are underused. A recent KFF analysis of 2024 Marketplace data found that insurers denied about 20% of claims overall, but fewer than 1% of denied claims were appealed. Among the appeals that were filed, insurers upheld the original denial about 66% of the time. That does not mean appeals are pointless. It often means the first appeal record was too thin, too late, or too disconnected from the plan’s stated reason.
One of the biggest mistakes is assuming the denial notice says everything you need to know.
Many notices use broad phrases like “not medically necessary,” “experimental,” “not consistent with clinical policy,” or “does not meet coverage criteria.” Those phrases can sound definitive, but they may leave out the exact policy, guideline, coding issue, or factual assumption behind the decision.
Under federal appeals rules, plans generally are expected to provide information about the basis for the denial and the appeal process. In ERISA-governed plans, claimants may also request relevant documents, including internal rules, guidelines, protocols, or similar criteria relied on in the decision, according to the U.S. Department of Labor’s claims-procedure FAQs. For ACA-regulated coverage, CMS explains that denial notices are intended to give consumers detailed information about the grounds for the denial and how to pursue review.
Here’s what this often means in practice: a patient appeals the phrase, but not the actual rationale.
A more effective appeal often starts by identifying the plan language, policy bulletin, or clinical criteria the reviewer actually used.