Insurance denials
Insurance denied for 'not medically necessary' — your appeal rights
When an insurer denies a claim as 'not medically necessary,' that's a determination — not a final answer. Federal law gives every covered patient the right to two levels of internal appeal and one independent external review. Most denials reversed on appeal involve documentation the insurer didn't have at the time of the initial decision.
Last reviewed May 2026 · MediBill Saver Editorial Team
Federal basis
ERISA + ACA appeals rights
ERISA §503 (29 USC §1133) / ACA §2719 (42 USC §300gg-19)
Read the source →What this looks like in practice
ERISA §503 (for employer plans) and ACA §2719 (for non-grandfathered individual / small group plans) require insurers to provide: (1) written denial with the specific reason and the claim file the insurer relied on, (2) at least one level of internal appeal (most plans offer two), (3) for non-grandfathered plans, an independent external review by a state-certified IRO or HHS-certified federal IRO. The plan must follow specific timelines: 30 days for pre-service decisions, 60 days for post-service. Appeals require the plan to consider any new evidence the patient submits.
The most successful appeal strategy: get the medical record, the claim file, and the relevant clinical guideline (LCD, NCD, or specialty society guideline), then write an appeal that maps the documented care to the criteria the insurer applied. Plans reverse a meaningful share of medical-necessity denials when presented with this kind of structured appeal.
How to spot it on a bill
- 01.Claim denied with a code like 'not medically necessary,' 'experimental/investigational,' or 'inappropriate setting.'
- 02.Initial denial letter cites a specific medical-necessity criterion.
- 03.Service was actually rendered and documented in the medical record.
What to write — ready-to-paste language
Replace the bracketed fields with your specific details. Send by certified mail with return receipt, or via the hospital’s patient portal if it offers documented messaging. Keep a copy.
I am appealing the denial of claim [number] for service on [date]. The denial cites [reason]. I have attached: (1) the relevant entries from my medical record showing the documented clinical indication, (2) the [LCD/NCD/specialty guideline] that establishes medical necessity for this indication, and (3) my treating provider's note explaining why the service was appropriate. Per ERISA §503 / ACA §2719, please review this appeal and respond within the regulatory timeline. If the appeal is denied at the internal level, please confirm my right to external review and the process for requesting it.
This is a starting point, not legal advice. Your specific situation may warrant additional details. Our audit drafts this letter automatically with your bill’s specifics filled in.
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Related scenarios
Service denied because prior authorization wasn't obtained
When the doctor's office didn't get prior auth and your insurance denies the claim, the hospital often bills the patient. Federal rules and many state laws push that liability back to the provider.
Step therapy denied — must try cheaper drug first
'Step therapy' or 'fail first' rules require trying a lower-cost drug before insurance covers a more expensive one. Federal and most state laws give patients a way to bypass when medically necessary.
Medicare Advantage denied a service Original Medicare would cover
Medicare Advantage plans (Part C) must cover everything Original Medicare covers — and OIG has flagged repeated patterns of inappropriate denials. The MA appeal process exists for exactly this.
Common questions
How long do I have to appeal?
Do I need a lawyer to appeal?
What happens if external review is denied?
P.S. The dispute language above is a starting point. Bills with this pattern often have additional issues alongside it — coding errors stacked with markup, surprise bills stacked with charity- care eligibility. The scan finds all of them in one pass. Start the audit →
P.P.S. Federal law gives you these rights regardless of how the bill arrived. Insured, uninsured, in-network, out-of-network — the underlying patient-protection statutes apply.
P.P.P.S. Bills are time-sensitive. Most insurance appeals must be filed within 180 days. Charity-care discounts at non-profit hospitals are most easily applied within 240 days of the original bill. Acting earlier costs less.