BACKGROUND: Gut dysbiosis is common in patients with chronic kidney disease (CKD) and is closely related to inflammatory processes. Some nutritional strategies, such as bioactive compounds present in curcumin, have been proposed as an option to modulate the gut microbiota and decrease the production of uremic toxins such as indoxyl sulfate (IS), p-cresyl sulfate (pCS) and indole-3 acetic acid (IAA). OBJECTIVE: To evaluate the effects of curcumin supplementation on uremic toxins plasma levels produced by gut microbiota in patients with CKD on hemodialysis (HD). METHODS: Randomized, double-blind trial in 28 patients [53.6 ± 13.4 years, fourteen men, BMI 26.7 ± 3.7 kg/m(2), dialysis vintage 37.5 (12-193) months]. Fourteen patients were randomly allocated to the curcumin group and received 100 mL of orange juice with 12 g carrot and 2.5 g of turmeric and 14 patients to the control group who received the same juice but without turmeric three times per week after HD sessions for three months. IS, pCS, IAA plasma levels were measured by reverse-phase high-performance liquid chromatography RESULTS: After three months of supplementation, the curcumin group showed a significant decrease in pCS plasma levels [from 32.4 (22.1-45.9) to 25.2 (17.9-37.9) mg/L, p = 0.009], which did not occur in the control group. No statistical difference was observed in IS and IAA levels in both groups. CONCLUSION: The oral supplementation of curcumin for three months seems to reduce p-CS plasma levels in HD patients, suggesting a gut microbiota modulation.