Inside UnitedHealth’s Effort to Deny Coverage for a Patient’s Care — ProPublica

More than 200 million Americans are covered by private health insurance. But data from state and federal regulators shows that insurers reject about 1 in 7 claims for treatment. Many people, faced with fighting insurance companies, simply give up: One study found that Americans file formal appeals on only 0.1% of claims denied by insurers under the Affordable Care Act. 

Insurers have wide discretion in crafting what is covered by their policies, beyond some basic services mandated by federal and state law. They often deny claims for services that they deem not "medically necessary."…

https://www.propublica.org/article/unitedhealth-healthcare-insurance-denial-ulcerative-colitis