Background: Chronic kidney disease (CKD) is characterized by distortion of fluid and electrolyte homeostasis, causing accumulation of fluid, toxins and electrolytes. Hemodialysis (HD) or kidney transplantation are the gold standard treatment strategies for end-stage CKD. The deterministic factor for optimal HD treatment, relies on the accurate estimation of the ultrafiltration (UF) volume based on patients’ pre-dialysis and target weight. However, this method lacks sensitivity, efficiency and reliability in assessing patients’ hydration status (i.e. euvolemic, hypovolemic or hypervolemic). A promising tool in assessing hemodynamic and volume status in patients with fluid overload is bio-impedance (BioZ). Objective: To investigate the relationship between BioZ and changes in fluid and electrolyte balance in CKD patients treated with HD using a wearable, non-invasive bio-impedance (BioZ) device from Imec (Eindhoven, The Netherlands). Materials: Patients (n=30) with a varying UF volume were included. The device was attached to the patient’s chest in a predefined electrode configuration and four to five measurements were performed during each HD session. Pearson correlation was used to assess the strength of the relationship between variables. Results: The mean UF volume was 1640.10±911.28 ml and the mean baseline thoracic BioZ was 47.64±22.69, which increased to 55.09±28.88 Ω at the end of the HD session. Results indicate a significant, very strong positive correlation between relative thoracic BioZ and UF volume (r= 0.73; p<0.01). The relationship between the UF volume and the BioZ signal at the lower leg was less strong (r=0.44; p<0.01). Conclusion: Current results indicate that the wearable BioZ device is capable of accurately tracking fluid changes during HD sessions, supporting its role in fluid overload management. Future work should focus on improving the estimation of the UF volume using BioZ and on in-home monitoring strategies for these patients.