Uromodulin (UMOD) is a protein synthesized exclusively by tubular epithelial cells in the kidney. Higher urinary UMOD levels appear to reflect kidney tubule functional mass based on their direct association with kidney size, indices of tubular function, and lower risk of kidney disease progression.1 Higher UMOD concentrations in both the blood and urine have each been associated with lower rates of cardiovascular disease (CVD), but largely in separate cohorts.2,3 Owing to degradation and aggregation during storage,4 as well as changes in concentration from hydration,5 there are practical challenges to using urine UMOD measurements.