Subclinical overhydration predicts lower time in range and greater glycemic variability in type 2 diabetes on hemodialysis

Overhydration may influence glycemic control in patients with type 2 diabetes (T2D) undergoing hemodialysis (HD). We investigated whether the extracellular-to-total body water ratio (ECW/TBW), a marker of fluid overload, is associated with Time in Range (TIR) and glucose variability (GV) in this population. Methods: In this prospective study, 61 insulin-treated T2D patients with end-stage kidney disease undergoing online hemodiafiltration (OL-HDF) underwent 20 days of continuous glucose monitoring (CGM). A ΔTIR > 5% between HD and non-HD days was defined as clinically relevant glycemic fluctuation. Hydration status was assessed using multifrequency bioimpedance analysis. Results: Patients with higher ECW/TBW ratios (> 0.395) showed worse glycemic control compared with those with lower ratios, including significantly lower TIR and higher mean glucose levels during both HD and non-HD days. Glycemic variability was also higher in the overhydrated group, with significantly increased standard deviation and coefficient of variation. In multivariable analysis, ECW/TBW ratio remained the only independent predictor of ΔTIR > 5% between HD and non-HD days (OR 6.99; 95% CI 1.91–25.66; p = 0.003). Linear regression analyses further demonstrated that higher ECW/TBW ratios were independently associated with lower TIR (B = − 637.7, p = 0.011). When interpreted per 0.01-unit increase in ECW/TBW ratio, this corresponds to an approximate 6.4% decrease in TIR. A higher ECW/TBW ratio was also associated with higher mean glucose (B = + 1346.6, p = 0.009) and greater glycemic variability measured by both standard deviation and coefficient of variation. Conclusion: Subclinical overhydration is independently associated with reduced TIR and increased glycemic variability in insulin-treated patients with T2D undergoing hemodialysis. These findings highlight the importance of assessing hydration status when optimizing glycemic management in this high-risk population.