Case Report: Daily water monitoring provides an evidence-based guide for safe and effective use of diuretics-a longitudinal study.

Heart failure (HF) management commonly relies on diuretics, yet standard fixed-dose regimens fail to adjust for daily fluid fluctuations, often leading to suboptimal management. Current tools lack the real-time precision needed to adjust therapy in response to these fluctuations. Bioelectrical impedance analysis (BIA) is a tool that can potentially provide personalized guidance for adjusting diuretic therapy, but its daily clinical utility remains limited. We present the case of an 85-year-old patient with chronic HF who performed daily BIA measurements to guide diuretics administration over 1,201 days. The patient adjusted diuretic administration in response to rises in body weight and extracellular water to total body water (ECW/TBW) ratio, indicating fluid accumulation beyond his baseline variability. The patient maintained full adherence to daily BIA monitoring. Despite using diuretics on only 9.2% of the days, fluid balance remained stable with no changes in cardiac, renal, or electrolyte parameters. Fluid retention resolved within 24 h following tailored diuretic intervention. Additionally, daily BIA facilitated differentiation between fluid-driven from non-fluid-driven weight changes, improving informed decision-making. This case demonstrates that a daily BIA-guided, patient-led diuretic regimen was feasible and effective in maintaining fluid stability with minimal diuretic use. This approach may serve as a personalized self-care model for chronic HF management.