AIMS: The rising prevalence of diabetes in young adults threatens global health and sustainable development. However, its full macroeconomic impact, especially the welfare losses beyond conventional productivity costs, has not been systematically quantified at a global level. We aimed to estimate the current and future global economic burden of diabetes in individuals aged 15-39 years using a welfare-based approach. METHODS: Using disability-adjusted life-years (DALYs) from the Global Burden of Disease Study 2021, we monetized health losses into a value of lost welfare (VLW) via a value of a statistical life year approach. We estimated the VLW globally, regionally and nationally, analysed its distribution by Socio-Demographic Index (SDI) and made projections to 2050. RESULTS: In 2021, the global economic burden was Int$1.16 trillion. Low-SDI regions had the highest relative burden (1.21% of GDP), whereas high-SDI regions had the largest absolute loss. Geographically, East Asia showed the highest absolute burden (Int$240.30 billion) and Oceania the highest relative impact (3.03% of GDP). Projections show the burden will more than double by 2050 to 1.32% of global GDP, driven almost entirely by type 2 diabetes. CONCLUSIONS: Diabetes in young adults represents a significant and growing macroeconomic burden. Our findings underscore the urgent need for public health strategies and economic policies focused on preventing type 2 diabetes. Such interventions are especially critical for countries with fragile health systems to mitigate substantial future economic and health losses.