How to appeal a "not medically necessary" denial

Health plans pay for care that is medically necessary. HealthCare.gov defines that as health care services or supplies needed to diagnose or treat an illness, injury, condition, disease or its symptoms and that meet accepted standards of medicine. Your plan document has its own definition, and the plan applies it using written clinical criteria.

A denial on these grounds means a reviewer compared the records the plan received against those criteria and decided something was missing. The gap can be clinical, or it can be in the paperwork: a test result that was never sent, a past treatment that is not in the notes, or symptoms described in different words than the criteria use.

Under federal claims rules for employer plans, the denial notice must give the specific reason for the denial and the plan provisions it relied on. For a medical necessity denial, the plan must also give you an explanation of the scientific or clinical judgment behind the decision, applied to your medical circumstances, or tell you that explanation is free on request. The same rules apply to insurers that sell individual coverage, including most Marketplace plans.

Before you or your doctor write anything, get the documents the plan used. In employer and individual plans, you are entitled to copies of all documents, records and other information relevant to your claim, upon request and free of charge. "Relevant" includes any statement of the plan's policy or guidance on the denied treatment for your diagnosis, whether or not the reviewer relied on it.

Put the request in writing, date it and keep a copy. Ask for:

• The specific clinical policy, guideline or criteria the plan applied. If the plan relied on one, it must give it to you or provide a copy free of charge on request.
• The reviewer's notes and the written explanation of the clinical judgment.
• The names or credentials of any medical experts the plan consulted. Employer plans must identify the medical experts whose advice they obtained.
• A list of every record the plan received from your doctors, so you can see what was missing.
• The diagnosis and treatment codes on the claim and their meanings, which plans must give you on request.

Keep an eye on the appeal deadline while you wait for the file. If it is getting close, file the appeal on time and send more documents as they arrive. For deadlines by plan type, see the pages for employer plans, Marketplace plans, Medicare Advantage, Original Medicare and Medicaid.

A letter from the treating doctor can answer the plan's criteria directly. HealthCare.gov's appeal guide suggests sending additional information such as a letter from the doctor, and employer plans must consider everything you submit, even if it was not part of the first decision.

The letter works best when it answers the plan's criteria one by one. Ask your doctor's office to include:

• Your diagnosis, using the same codes as the claim.
• Your history with the condition: how long you have had it, how severe it is, and what has changed.
• Treatments already tried, with dates, doses and results, including side effects and reasons a treatment could not be used.
• Why this service, in this setting and at this level of care, is needed now, and what the doctor expects without it.
• Each criterion in the plan's policy, with the matching evidence from your records.
• Any published clinical guidelines or studies the doctor relies on.

Attach the records the letter mentions: office notes, test results, imaging reports and pharmacy history. A letter that says the care is necessary without tying it to the criteria gives the reviewer little new to weigh.

Some plans let your doctor request a peer-to-peer review, a phone call with a physician reviewer at the plan. Plans set their own rules for when these calls are offered and how fast they must be requested, so ask your doctor's office to check as soon as the denial arrives.

A call after a written denial may not change it. One Medicare Advantage plan told providers in 2026 that its post-denial calls are informational only and cannot change the outcome. If the call does not settle the matter, keep the written appeal on schedule.

Clinicians are supposed to be involved either way. In Medicare Advantage, a planned medical necessity denial must be reviewed by a physician or other appropriate health care professional with expertise in the field before it is issued. In an employer plan appeal, the plan must consult a health care professional with appropriate training and experience in the field of medicine involved.

If the plan upholds the denial, you can usually ask for an external review, in which an independent review organization decides. Federal rules make external review available for denials that involve medical judgment, including the plan's requirements for medical necessity, appropriateness, health care setting, level of care, or effectiveness of a covered benefit. The Labor Department's rule for employer plans uses the same scope.

The plan must follow the result: your insurer is required by law to accept the external reviewer's decision. If waiting would put your health at risk, ask for an expedited review. In urgent situations, you can request external review before the internal appeal is finished.

Medicare Advantage has its own path: if the plan upholds its denial, it automatically forwards the case to an Independent Review Entity. The route and the deadlines differ by plan type, so check the pages for employer plans, Marketplace plans, Medicare Advantage, Original Medicare and Medicaid.

Medicare Advantage plans must follow Medicare's national and local coverage decisions and the general coverage and benefit conditions in Traditional Medicare law. A plan may write its own criteria only when Medicare's coverage criteria are not fully established, and it must post those internal criteria publicly, with a summary of the evidence behind them.

The plan must also weigh your medical history, your doctor's recommendations and clinical notes. In your appeal, ask which Medicare rule or internal policy the plan applied. If it used its own policy, ask where the public version is posted and whether Medicare already has a coverage rule for the service.

If the plan approved the service in advance, it generally may not deny coverage later for lack of medical necessity. See appealing a Medicare Advantage denial for deadlines.