<p>The concept of permittivity properties of dialysate allows the use of electromagnetic sensing techniques in hemodialysis treatment. In this study, we have introduced a method for assessing the adequacy of dialysis, which is based on the dialysate approach. The dialysate-based method offers several advantages, including preventing blood contamination, the absence of the need for the patient’s blood, and convenient application within laboratory settings. The dielectric properties of the dialysis fluid were analyzed using the open-ended coaxial probe technique to investigate the impact of various urea levels. The findings revealed a direct correlation between fluctuations in complex permittivity measurement and urea concentration levels. The measured results can be used to design invasive and non-invasive microwave sensors. However, further practical trials on dialysis fluid are needed.</p>