This single-center randomized controlled trial evaluated the effects of natural probiotic and synbiotic supplementation on clinical and biochemical characteristics in adults with end-stage renal disease receiving maintenance hemodialysis at the Urology and Nephrology Center, Mansoura University, Egypt. Participants were randomized into three groups (control, probiotic, and synbiotic), with supplementation given for 6 months in the intervention groups. The study assessed changes in uremic toxins (including p-cresyl sulfate) as the primary outcome, and cardiovascular parameters, quality of life, and cognitive function as secondary outcomes. The trial aimed to determine whether modulation of gut microbiota with probiotics or synbiotics can improve outcomes in hemodialysis patients