How to Appeal an Insurance Denial (Step by Step)
About 40% of denied insurance claims are reversed on appeal — but most people never appeal. Here's exactly how to fight back, what to include, and which deadlines matter.
Why appeals get reversed so often
First-level insurance denials are frequently administrative decisions made by algorithms or junior reviewers who never examined your specific situation. Studies show approximately 40% of denied claims are reversed on internal appeal when a human reviews the case. Insurers count on the fact that most people don't appeal.
The most common reason appeals succeed: a physician provides a letter of medical necessity that the initial reviewer never had access to.
Types of denials and how to approach each
Get a letter of medical necessity from your physician. Include clinical guidelines from medical specialty societies supporting the treatment.
If your doctor failed to get prior auth, appeal on medical necessity grounds. If you got auth and they still denied, cite the authorization number explicitly.
Check if the No Surprises Act applies. If not, appeal for a "gap exception" if no in-network provider was reasonably available.
Find peer-reviewed studies and clinical guidelines supporting the treatment. Cite that the treatment is accepted standard of care.
Review your plan documents carefully. Denials sometimes cite the wrong benefit category. If genuinely not covered, explore external review on medical necessity grounds.
Your ACA appeal rights and deadlines
Under the ACA, you have the right to an internal appeal of any adverse benefit determination. You have 180 days from the denial notice to file. Insurer must respond within 60 days for standard appeals, or 72 hours for urgent/expedited appeals.
File within 180 days of denial. Insurer must respond within 60 days. Use for non-urgent treatment or prescription denials.
For ongoing care or urgent situations. Insurer must respond within 72 hours. Mark your appeal as urgent explicitly in the letter.
What to include in your appeal letter
Quote the denial letter directly — claim number, date, and stated reason for denial.
The single most important piece of evidence. Your doctor states why this specific treatment is medically necessary for your specific condition.
Guidelines from medical specialty societies (AHA, ACS, ASCO, etc.) carry significant weight with medical reviewers.
Explicitly invoke your right to a full and fair internal review under the ACA.
60 days for standard, 72 hours if urgent. Name what you will do if they miss it: file with your state DOI.
External review — when internal appeal fails
If your internal appeal is denied, you have the right to an external independent review. The external reviewer's decision is binding on the insurer — they must comply even if they disagree. Request external review through your state Department of Insurance. Most states complete external reviews within 45 days (72 hours for urgent). Roughly 40% of externally reviewed denials are overturned.
A physician letter of medical necessity turns a generic appeal into a clinical argument insurers cannot easily dismiss. Get the physician letter first, then write the appeal citing ACA § 2719 and the 60-day response deadline.
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LetterPerfect is not a law firm. This guide is for informational purposes only and does not constitute legal advice. For legal representation, consult a licensed attorney in your state.