Functional diarrhea (FDr) is one of Disorders of gut-brain interaction (DGBI) characterized by recurrent loose or watery stools without predominant abdominal pain or bloating. It is distinct from Irritable bowel syndrome with diarrhea (IBS-D), which includes abdominal pain as a key diagnostic criterion.​ FDr is diagnosed using the Rome IV criteria, requiring symptoms for at least six months and excluding IBS-D. Epidemiological studies report prevalence rates ranging from 1.5% to 17%, but research on its pathophysiology remains limited. Potential mechanisms include gut-brain axis dysfunction, bile acid levels, and psychosocial factors, though these are less pronounced compared to IBS-D. Differential diagnosis is essential to exclude conditions such as infections, inflammatory bowel disease, celiac disease, food intolerances, and bile acid malabsorption. ​Diagnostic tools include stool tests, endoscopy, and biochemical evaluations. Treatment options are limited and often align with IBS-D management strategies, including dietary modifications like a low-FODMAP diet, probiotics, Loperamide, and Ramosetron. ​Antibiotics such as Rifaximin may also be effective. Given the overlap in symptoms between FDr and IBS-D, treatments for IBS-D may be applicable to FDr. ​However, further research is needed to better understand its pathophysiology and develop targeted therapies. Comprehensive differential diagnosis remains essential for accurate identification and management.