This article investigates demand-side efficiency in global health—or the efficiency with which health system users convert public health resources into health outcomes. We introduce and explain the concept of demand-side efficiency as well as quantitative methods to empirically estimate it. Using a robust nonparametric form of technical efficiency analysis, we estimate demand side efficiency and its social determinants. We pilot these methods looking at how efficiently pregnant women in Northern Vietnam convert public health resources into appropriate maternal care as defined by national policy. We find that women who live in non-mountainous geographies, who are formally employed, who are pregnant with a boy and who are ethnic minorities are all more likely to be efficient at achieving appropriate care. We find no significant association between wealth or education and efficiency. Our results suggest that, in the Vietnamese context, women who are the most likely to achieve appropriate maternal care, are not necessarily the most likely to do so efficiently. Women who live in non-mountainous geographies and who are formally employed are both more likely to achieve appropriate care and to do so efficiently. Yet ethnic minority women, who do not systematically achieve better care, are more likely to be efficient or to achieve better care when compared with those with the same endowment of public health resources. On the methodological level, the pilot highlights that this approach can provide useful information for policy by identifying which groups of people are more and less likely to be efficient. By understanding which groups are more likely to be efficient—and in turn how and why—it may be possible to devise policies to promote the drivers of, or conversely address the constraints to, optimizing demand-side efficiency.