This study investigates the determinants of supplemental coverage and flexible spending accounts (FSAs) enrollments among US health care consumers. It does so using a pooled cross-section of the 2015-2016 national health interview surveys (NHIS), along with (semi)parametric bi-variate probit modeling methods. We find that supplemental coverage and FSAs are complement health solutions with a positive 14.7% correlation. The findings also emphasize that the most important trigger factors influencing the joint probability of supplemental coverage and FSAs enrollment include not only the paid premium for basic coverage, but also age, education, marital status, number of work hours, region of residency, citizenship status, and annual health expenditure level. It is also found that controlling for these latter factors, health status fails to significantly influence FSAs enrollment decisions. Furthermore, despite the fact that the relative frequency of individuals with FSAs rises with increasing levels of medical expenditure, individuals with greater medical care spending are found to have a lesser likelihood of FSAs enrollment in the USA.