Background: Kuwait operates a state-funded universal healthcare system serving a population that is 70% expatriate, yet existing health financing data aggregate out-of-pocket (OOP) expenditure across citizen and non-citizen populations, obscuring significant distributional inequalities. No published study has disaggregated Kuwait's OOP burden by population segment or evaluated the financial protection adequacy of Kuwait's mandatory health insurance framework for expatriates. This gap has become critically policy-relevant following the December 2025 doubling of mandatory health insurance premiums and the ongoing implementation of the Health Assurance Hospitals Company (Dhaman) reform. Methods: A secondary analysis was conducted using the WHO Global Health Expenditure Database, World Bank national accounts, Kuwait Central Statistics Bureau household expenditure survey data, and published government policy documents covering 2010–2023. Three analytical components were undertaken: (1) a trend analysis of OOP as a share of current health expenditure (CHE) benchmarked against five Gulf Cooperation Council (GCC) comparator countries; (2) modeled estimation of catastrophic health expenditure (CHE) incidence across household income deciles using the Xu et al. framework (OOP >10% of household consumption) with income elasticity sensitivity analysis (ε=0.6–1.0); and (3) a scenario-based financial protection adequacy assessment of three mandatory insurance configurations. Results: Kuwait's aggregate OOP share rose from 8.3% of CHE in 2010 to 11.5% in 2022, then declined to an estimated 10.0% in 2023. In absolute terms, OOP expenditure grew from KD 94 million in 2010 to KD 278 million in 2022, a nominal increase of 195.7%. Modeled CHE incidence in the lowest household income decile is estimated at 18–23%, substantially exceeding the WHO 10% threshold. Scenario analysis demonstrates that under the proposed Dhaman premium trajectory (KD 130–190 annually), low-income expatriate households in the first consumption decile would face total annual OOP burdens equivalent to 23–27% of household consumption — significantly above the catastrophic threshold at every stage of the reform pathway. Conclusions: Kuwait's mandatory insurance reform provides meaningful financial protection for median and above-median income expatriate households but does not resolve the financial protection deficit for the lowest income quartile. Three evidence-based policy recommendations are proposed: income-tiered premiums scaled to employment category; an essential services floor guarantee for low-wage workers; and a hardship waiver mechanism. Findings are applicable across all six GCC states, which share analogous structural health financing characteristics.