A denied health insurance claim isn't necessarily final — federal law guarantees a two-stage appeals process, and insurers are legally required to let you use it. * The first stage is an internal appeal, reviewed by your own insurance company. You have 180 days from the date you receive the denial notice to file it, and your appeal generally works best as a detailed letter explaining specifically why the claim should be covered under your policy, backed by supporting evidence like medical records, test results, or a letter from your doctor. Insurers have to respond within specific windows: 30 days if the disputed care hasn't happened yet, or 60 days if you've already received it. * If the internal appeal doesn't go your way, the second stage is an external review, handled by an independent reviewer with no connection to your insurance company. You have to request it within 4 months of your final internal denial. Eligible denials include disputes over medical necessity, whether a treatment counts as "experimental," and coverage cancellations your insurer claims are due to incomplete or false information on your original application. * Cost is rarely a barrier: if your external review goes through the federal government's process, it's free. Even through a state process or independent review organization, the charge can't legally exceed $25. * The external reviewer's decision isn't just a recommendation — insurers are legally required to accept it. If you need help navigating either stage, your state's Consumer Assistance Program or Department of Insurance can walk you through the paperwork at no cost.