Small Bowel Diseases & Malabsorption encompass a diverse group of disorders that impair digestion and nutrient absorption within the small intestine, leading to significant nutritional deficiencies and systemic complications. The small bowel plays a central role in the absorption of macronutrients, micronutrients, vitamins, and minerals, and any disruption in its structure or function can result in malabsorption syndromes. Common causes include celiac disease, Crohn’s disease involving the small intestine, tropical sprue, small intestinal bacterial overgrowth, short bowel syndrome, and infectious or inflammatory enteropathies. Patients with malabsorption often present with chronic diarrhea, weight loss, steatorrhea, anemia, fatigue, and deficiencies of fat-soluble vitamins, iron, folate, and vitamin B12. The underlying mechanisms vary and may involve mucosal inflammation or atrophy, enzymatic defects, impaired bile acid function, altered gut motility, or disruption of the intestinal microbiome. Accurate diagnosis requires a thorough clinical evaluation supported by laboratory testing, serology, breath tests, stool studies, imaging, endoscopy, and histopathological assessment when needed.