IRCT20260315068995N1 IRCT 2026-04-13 Tehran University of Medical Sciences Gut Microbiome Composition and Response to Probiotic Intervention in Patients with Fibromyalgia using a Neurobiological Approach Gut Microbiome Composition and Response to Probiotic Intervention in Patients with Fibromyalgia using a Neurobiological Approach 2026-05-22 anticipated 42 Recruiting https://irct.ir/trial/89343 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Crossover, Purpose: Health service research, Randomization description: 1.Details of the Randomization Process: In this study, randomization is performed by allocating patients to intervention and control groups using random blocks in a 1:1 ratio. This method ensures that the distribution of patients in each group is random and unbiased. 2.Linguistic Consistency on Both Sides: In the design and reporting of this study, all terms and expressions have been applied consistently and harmoniously on both sides to ensure that there is no ambiguity in the interpretation of the results. 3.Randomization Method: In this study, the randomization method is precisely determined by allocating patients using random blocks and implementing double blinding (so that both patients and researchers are unaware of group assignments). Additionally, the supplements are coded and packaged by an independent individual to prevent any bias, Blinding description: Description of the Blinding Method: In this study, double blinding is fully implemented. This means that both patients and researchers will be unaware of group assignments. Patients are randomly allocated to the intervention and control groups, and all information related to the groups is managed in a coded manner by an independent individual. This person is responsible for the packaging and distribution of the supplements, ensuring that they have no knowledge of the type of intervention the patients receive. This approach ensures that there is no bias in the assessment of the results. Linguistic Consistency on Both Sides: All terms and expressions have been used consistently and harmoniously on both sides (Persian and English) to ensure that there is no ambiguity in the interpretation of the findings. N/A Fibromyalgia. Intervention group: In interventional phase , eligible patients were divided into two groups : intervention and control groups using randomized block design with 1 : 1 ratio .two - way کورسازی is done by the codification of supplements and the use of an independent individual to manage allocation .. No - There is not a plan to make this available Justification or reason for not sharing IPD is I haven 't decided yet - the release schedule is not yet clear .