ObjectivesWe aimed to determine: (1) the prevalence and socio-economic distribution of undiagnosed, untreated, and uncontrolled diabetes mellitus (DM); (2) the relationship between socio-economic status (SES) and undiagnosed, untreated, and uncontrolled DM; and (3) if this relationship is mediated by gender. Study designCross-sectional nationally representative household-based survey. MethodsWe used data from the Bangladesh Demographic Health Survey from 2017 to 18. Our findings were based on the responses of 12,144 individuals aged 18 years and older. As a measure of SES, we focused on standard of living (hereinafter referred to as wealth). The study's outcome variables were prevalence of total (diagnosed + undiagnosed), undiagnosed, untreated, and uncontrolled DM. We used three regression-based approaches—adjusted odds ratio, relative inequality index, and slope inequality index—to assess different aspects of SES differences in the prevalence of total, undiagnosed, untreated, and uncontrolled DM. We used logistic regression analysis to look at the adjusted association between SES and the outcomes after gender stratification to see whether gender status moderates the association between SES and the targeted outcomes. ResultsIn our sample analysis, the age-adjusted prevalence of total, undiagnosed, untreated, and uncontrolled DM was 9.1%, 61.4%, 64.7%, and 72.1%, respectively. Females had a higher prevalence of DM and undiagnosed, untreated, and uncontrolled DM than males. When compared to people in the poor SES group, people in the rich and middle SES groups had 2.60 times (95% confidence interval [CI] 2.05–3.29) and 1.47 times (95% CI 1.18–1.83) higher chance of developing DM. When compared to individuals in the poor SES group, those in the rich SES groups were 0.50 (95% CI 0.33–0.77) and 0.55 times (95% CI 0.36–0.85) less likely to have undiagnosed and untreated DM. ConclusionsIn Bangladesh, rich SES groups were more likely than poor SES groups to have DM, whereas poor SES groups with DM were less likely than rich SES groups to be aware of their disease and obtain treatment. The government and other concerned parties are urged by this study to pay more attention to developing suitable policy measures to reduce the risk of DM, particularly among rich SES groups, as well as targeted efforts to screen for and diagnose DM in socio-economically disadvantaged groups.