When Daniel spent years seeking diagnosis for his spinal cyst, he faced denial after denial and only felt compelled to fight his insurer because he had a family to support. Through survey and interview evidence, this chapter explores who is most vulnerable to being denied coverage by health insurers, and what accounts for these vulnerabilities. Highlighting the first patient-level analysis of coverage denials across public and private insurance, this chapter shows that those from marginalized groups – namely, women, LGBTQ patients, and those in worse health – are more vulnerable to experiencing coverage denials. Interestingly, though low health literacy might be expected to lead some patients to pursue care outside their insurance benefits, socioeconomic factors do not consistently correlate with greater vulnerability to coverage denial. This finding offers insights into the scope of defensive medicine amid medical malpractice concerns. Black and Hispanic patients appear to be particularly likely to experience repeated coverage denials, and, given the significant health literacy demands of appealing, patients from marginalized groups may be particularly ill-equipped to weather the storm.