The aim of this single-blind, randomized, experimental study was to investigate the effect of Rubus sanctus root extract, which has antioxidant properties, added to the routine diet of patients with Graves' disease on the prognosis of the disease. The study sample included patients who presented to the Endocrinology and Metabolic Diseases Outpatient Clinic of Muğla Sıtkı Koçman University Training and Research Hospital and were diagnosed with Graves' disease or developed a relapse after necessary examinations. Cohen's standardized effect size was used. Accordingly, the required sample size for the study was determined to be 42, using an alpha value of 0.05, an effect size of 0.80, and a theoretical power of 80%. The study planned to include a minimum of 42 participants: 21 intervention participants and 21 controls. Patients assigned to the control group were asked to continue their routine diet, adhere to any necessary pharmacological treatments, and consume a placebo tea for the planned 8-week intervention period. Routine monthly examinations will be collected, and anthropometric measurements will be repeated at the end of 8 weeks. Patients assigned to the experimental group will be asked to continue their routine diet for 8 weeks, comply with any required pharmacological treatments, and consume Rubus sanctus root extract, produced by aqueous extraction and lyophilization, with active ingredient (phenolic compound) determined by LC-MS-MS, and prepared as a tea in 5-g packets. Anthropometric measurements will be repeated at the end of 8 weeks. H0: Rubus sanctus root extract supplemented to the diet has no effect on Graves' disease. H1: Rubus sanctus root extract supplemented to the diet has an effect on Graves' disease.