Roughly one in seven health insurance claims is denied. If your claim is denied, challenge it. First check the reason listed on the Explanation of Benefits notice you received, and if you need more clarification, call your insurance’s customer-service number. The denial might be the result of an administrative error that can be corrected over the phone. If this fails, send a written request for a formal review. If you’re still not satisfied, contact your state department of insurance or managed health care to file a complaint. To prevent denied claims from the start, always check your insurance coverage before having any tests or health services performed.