BackgroundThe goal of universal health coverage is challenging for chronically under-resourced health systems. Although household out-of-pocket payments are the most important source of health financing in low-income countries, relatively little is known about the drivers of primary health care expenditure and the predictability of the burden associated with high fee-for-service payments. This study describes out-of-pocket health expenditure and investigates demand- and supply-side drivers of excessive costs in the Democratic Republic of Congo (DRC), a central African country in the midst of a process of reforming its health financing system towards universal health coverage.MethodsA population-based household survey was conducted in four provinces of the DRC in 2014. Data included type, level and utilization of health care services, accessibility to care, patient satisfaction and disaggregated health care expenditure. Multivariate logistic regressions of excessive expenditure for outpatient care using alternative thresholds were performed to explore the incidence and predictors of atypically high expenditure incurred by individuals.ResultsOver 17% (17.5%) of individuals living in sample households reported an illness or injury without being hospitalized. Of 3341 individuals reporting an event in the four-week period prior to the survey, 65.6% sought outpatient care with an average of one visit (SD = 0.0). The overall mean expenditure per visit was US$ 6.7 (SD = 10.4) with 29.4% incurring excessive expenditure. The main predictors of a financial risk burden included utilizing public services offering the complementary benefit package, dissatisfaction with care received, being a member of a large household, expenditure composition, severity of illness, residence and wealth (p < .05). The insured status influenced the expenditure level, with no association with catastrophe. Those who did not seek care when needed reported financial constraints as the major reason for postponing or foregoing care. Wealth-related inequities were found in service and population coverage and in out-of-pocket payment for outpatient care.ConclusionBurdensome expenditure for primary care and its key drivers are of utmost importance. Forthcoming health financing reform agendas must incorporate a strategy for getting data used in the design of financial risk protection. Realizing equitable and efficient access to outpatient care is a vital ingredient for sustainable health systems.