"Not Medically Necessary": What That Letter Actually Means and How to Fight It

Four words that change everything: not medically necessary. Your doctor recommended the surgery. You and your doctor agreed it was the right course of treatment. And then a person at your insurance company — often a nurse reviewer who has never examined you — overruled your doctor with a form letter.

This is the most common reason for surgical denials in the United States. Understanding what it actually means, and how the appeal process works, gives you a real chance at reversal — and a clear picture of your alternatives if the appeal fails.

What "not medically necessary" actually means

In insurance language, "medically necessary" has a specific contractual definition — and it is narrower than what your doctor considers necessary. Your insurer's definition typically requires that the procedure be "appropriate for the diagnosis," "not primarily for convenience," "consistent with generally accepted standards of medical practice," and "the most cost-effective option that adequately addresses the condition."

That last criterion is where most denials happen. Your surgeon recommends a total knee replacement. The insurer says physical therapy, injections, and weight management are less expensive interventions that have not been exhausted. The surgery may be medically appropriate — but until you have documented failure of conservative treatments, it is not "medically necessary" under the contract.

The frustrating reality: the insurer is often technically correct under the policy language, even when the denial feels wrong. The appeal is not about proving your doctor is right — it is about proving, with documentation, that the insurer's preferred alternatives have been tried and failed.

The three-level appeal

Level 1: Internal appeal

You have 180 days from the denial to file. Submit a letter from your treating physician explaining why the procedure is necessary, documentation of failed conservative treatments, relevant medical records and imaging, and any peer-reviewed guidelines supporting the intervention. Insurers overturn roughly 40 to 60 percent of internal appeals that include physician-authored letters of medical necessity with supporting documentation.

Level 2: Second internal appeal

If the first appeal is denied, most plans allow a second review by a different reviewer. This is your opportunity to address the specific reasons cited in the first denial. If the denial said "insufficient trial of physical therapy," submit PT records documenting the trial and its failure.

Level 3: External review

If internal appeals fail, federal law (the ACA) guarantees the right to an independent external review by a physician reviewer who is not employed by your insurer. External reviewers overturn insurer denials in roughly 40 to 50 percent of cases — a remarkably high rate that suggests many denials do not survive independent scrutiny. The external review decision is binding on the insurer.

When the appeal fails: your options

If all three levels of appeal fail, you have concrete alternatives. Cash-pay pricing at US facilities is often 30 to 50 percent below the insurer's billed rate. Medical tourism to Colombia can reduce costs by 50 to 70 percent compared to US cash-pay. HSA and FSA funds can be applied to the out-of-pocket cost. And medical financing is available, though interest rates vary widely.

For a complete overview of every path forward after a denial, see Your Surgery Was Denied: Every Option You Have.