Step 1: Read the denial letter — every word matters
Your denial letter is a legal document. Under ACA requirements, it must include the specific reason for denial, the clinical criteria or plan provision used to deny the claim, instructions on how to appeal, the deadline to file an appeal, and contact information for the insurer's appeals department. Write down: the exact denial reason (not your interpretation of it — the verbatim language), the claim number, the service date, and the appeal deadline. These four pieces of information are the foundation of your entire response.
Common denial reasons and what they mean
"Not medically necessary" means the insurer's reviewers decided the service didn't meet their clinical criteria for coverage — this is the most common denial reason and the most frequently overturned. "Prior authorization required" means the service was performed without advance insurer approval — these can sometimes be appealed retroactively, especially for emergency care. "Service not covered" means the plan excludes the service — sometimes this is legitimate, but sometimes it's a misclassification that can be corrected. "Step therapy required" means the insurer wants you to try cheaper alternatives first.
Step 2: Request the clinical criteria used to deny your claim
Call your insurer's member services line (the number on your insurance card) and ask them to send you, in writing, the specific clinical review criteria they used to deny your claim. They are legally required to provide this under ACA rules. This document — often from companies like Milliman (MCG), InterQual, or the insurer's internal medical policies — is your roadmap for the appeal. Your doctor's rebuttal needs to directly address these criteria and show why you meet them or why they were misapplied to your case.
Step 3: Do not pay the bill yet
If you received both a denial notice and a bill for the same service, do not pay the bill before you've explored your appeal options. Paying does not waive your right to appeal, but it can complicate the process and reduce urgency. Contact the provider's billing department and explain that you are actively appealing the insurance denial. Most providers will put the bill on hold for 30-90 days while a legitimate appeal is pending. If the bill is already in collections, dispute it in writing immediately and note that the underlying insurance claim is under appeal.
Step 4: File the internal appeal with complete documentation
This is where most patients either win or lose their appeal. A complete internal appeal includes: (1) a cover letter citing the denial reason and explaining specifically why it was wrong, (2) a letter of medical necessity from your treating physician that addresses the insurer's specific clinical criteria, (3) your relevant medical records (chart notes, labs, imaging), (4) documentation of any prior treatments tried, and (5) references to clinical practice guidelines supporting your treatment. Send via certified mail to the address listed in the denial letter.
What to do if your doctor won't write an appeal letter
Some doctors are unfamiliar with insurance appeals or too busy to help. Try asking a specialist or second provider. If you're using a primary care physician, ask for a referral to a specialist who deals with your condition regularly — specialists are often more experienced with appeals for specific treatments. You can also provide your doctor with a draft letter that they can review and sign, based on the clinical criteria the insurer provided.
Step 5: Escalate to external review if needed
If your internal appeal is denied, don't stop. The external review process — where an independent medical reviewer, not an insurer employee, decides your case — reverses denials 40-60% of the time. File for external review within 60 days of receiving your internal appeal denial. Contact your state insurance commissioner's office to find your state's external review process. For employer-sponsored plans that are "self-funded," you may need to use the federal external review process instead — the insurer's denial letter should clarify which process applies.
When to file a complaint with your state insurance commissioner
File a complaint with your state insurance commissioner when: the insurer missed an appeal deadline, the insurer failed to provide specific denial reasons, you believe the denial violates state insurance laws (like step therapy protections or mental health parity), or the denial is causing an urgent health situation. State commissioner complaints are free, create an official record, and can sometimes prompt direct intervention. California's DMHC and New York's DFS are particularly active in resolving patient insurance disputes.